(FORTUNE Magazine) – Not long ago real-life lobbyists looked and acted like their caricatures: fat, cigar-smoking men who shoved hundred-dollar bills into the pockets of lawmakers. Nowadays a few people still fit that description, and they're fun to have lunch with. But they don't hold much sway. Nor does the fancy-but-phony technique that began to replace these glad-handers a decade ago: rallying constituents through "grassroots" telemarketing--sometimes derided as AstroTurf lobbying because of its artificial nature. Not even the greenest intern on Capitol Hill is fooled when a thousand identical postcards or a hundred phone calls patched through from a telephone bank arrive in the office the same day.

The New Lobbying is more subtle--so subtle that Washington's most powerful interest groups can barely be found inside the Beltway. They still have offices, of course, but they're increasingly inhabited by researchers rather than by high-priced lobbyists. Their clout springs from the sincere support they get from actual voters back home, not from their ability to buy the right politicians or to pretend that a last-minute deluge of phone calls constitutes a groundswell. Call it the iceberg principle of legislative success: The powerhouses of persuasion aren't very visible above the Washington waterline, but they are very big, and very menacing.

That's just one of the conclusions gleaned from FORTUNE's new survey of clout in the capital: Washington's Power 25--an authoritative, impartial, empirical survey of the trade associations, labor unions, and other pressure groups that wield the greatest influence on the nation's legislative system. With the help of two up-and-coming polltakers--Democrat Mark Mellman of the Mellman Group and Republican Bill McInturff of Public Opinion Strategies--we asked nearly 2,200 insiders, including members of Congress, their staffs, and senior White House officials, to rank the mightiest lobbying groups (for a list of the 95 runners-up and the survey methodology, see page 158. We also asked them what works and what doesn't in the lobbyist's bag of tricks.

The Power 25 is a highly eclectic--almost curious--collection. From the 33-million-member American Association of Retired Persons, which polled No. 1 (to no one's surprise), to the ever controversial International Brotherhood of Teamsters (No. 25), and from the calculatedly quiet American Israel Public Affairs Committee (a remarkable No. 2) to the newly emergent National Restaurant Association (No. 24), the Washington 25 is as diverse as the nation itself. But it is more than that. It is a crystalline reminder that Alexis de Tocqueville was right more than 150 years ago when he observed that Americans were inveterate joiners who liked to cluster themselves into quasi-political volunteer groups.

Our survey rebuts one of the oldest axioms of lobbying: that campaign contributions buy power in Washington. While donations are still crucial (and are often abused, as the recent revelations about "soft money" excesses in the last presidential election show), they aren't the only keys to the kingdom. True, three of the top ten organizations owe their high rankings to their substantial campaign contributions: the Association of Trial Lawyers of America (No. 5), the American Israel Public Affairs Committee, and the American Medical Association (No. 8). But these days, interest organizations are valued more for the votes they can deliver. Most of the Power 25 have large numbers of geographically dispersed and politically active members who focus their energies on a narrow range of issues. In other words, they know their convictions and vote them. In this era of low voter turnout, that kind of commitment can mean the difference between victory and defeat in close elections, which translates into real heft on the legislative front. Few things are more important to a Congressman than getting reelected.

Fully half of the top ten groups in the FORTUNE survey were propelled there on the strength of their long-established grassroots networks. These kings of the town hall meeting are the American Association of Retired Persons; the National Federation of Independent Business, better known as the small-business lobby (No. 4); the National Rifle Association (No. 6); the Christian Coalition (No. 7); and the National Right to Life Committee (No. 10). Which isn't to say that money doesn't talk at all anymore. The AFL-CIO (No. 3) garnered great grades for both its grassroots and its campaign fundraising.

The affluence of an organization's members doesn't guarantee influence. Sometimes it has the opposite effect. In one of the most striking examples of the populist imperative, the only investor-related organization that made the Power 25 is the American Bankers Association at No. 12. The other financial services lobbies are washouts. The National Association of Securities Dealers is No. 83; the Public Securities Association, recently renamed the Bond Market Association, is No. 84; the Securities Industry Association is No. 47; and worst of all, the Investment Company Institute, the mutual fund industry trade association, languishes at No. 115. Of course these groups do more than try to affect laws and regulations; they also serve their own members. But one thing's for sure: Wall Street's stock isn't very high on K Street.

In contrast, the groups with huge memberships that also have an intense self-interest in government payouts are disproportionately represented in the Power 25. These include the National Education Association (No. 9) and AFSCME, the American Federation of State, County, and Municipal Employees (No. 14), whose members rely on government for their paychecks. More to the point are the Veterans of Foreign Wars (No. 16) and the American Legion (No. 23), whose members not only get veterans' benefits but also have a patriotic pull on politicians.

Populism is not the same as liberalism. The survey shows how narrowly the political spectrum is concentrated at the moderate center and the right. Only four of the Power 25 are labor unions. What's more, ideologically conservative interest groups outrank their left-leaning counterparts. The pro-gun National Rifle Association is No. 6, while its gun-control nemesis, Handgun Control Inc., is No. 68. The lately more moderate AARP is No. 1, while its stridently pro-subsidy competitor, the National Committee to Preserve Social Security and Medicare, is No. 35. And the antiabortion National Right to Life Committee is No. 10, while the pro-choice National Abortion and Reproductive Rights Action League, or NARAL, is lost in the crowd at No. 43. Why? Maybe it's because conservative groups often are better funded or that their members are more intensely committed to their cause. Or maybe the reason is that Republicans control Congress.

Another question: Why do the environmentalists and the so-called citizens' lobbies rank so low? Among the greens, the most influential is the Sierra Club at a mediocre No. 37. The other environmentalists are lower still. The League of Conservation Voters is No. 71, the Natural Resources Defense Council is No. 79, the Environmental Defense Fund is No. 86, and the National Wildlife Federation is No. 88.

It's the same story for the "good government" groups. The star of that category is one of Hillary Clinton's favorite lobbies, the Children's Defense Fund, which is also popular with Democrats in general. Yet it ranks only No. 40 overall, and the others fare even worse. The League of Women Voters is No. 93, Common Cause is No. 91, Ralph Nader's Public Citizen is No. 111, and the Center for Science in the Public Interest held up the bottom at No. 120. Concludes Mellman, FORTUNE's Democratic polltaker: "Some of these groups have neither the financial nor the grassroots clout they used to."

At the same time, some of the most talked-about tyros on the lobbying scene from the political right also posted disappointing results. The twin titans of the Republicans' antigovernment movement are located not at the apex but in the dreary middle of FORTUNE's list: Citizens for a Sound Economy is No. 62 and Americans for Tax Reform, famous for its Leave Us Alone coalition, is No. 66. The lesson: It takes both time and more than a modicum of support from politicians in both political parties for an interest group to gain any real standing in the hidebound world of Washington.

In addition to asking who works best and most effectively, our survey asked about what works. In many ways the basic lobbying campaign remains starchily standard: access lobbyists in Washington, grassroots lobbyists at home, publicists for free media, advertisers for paid commercials, and scholars to shape the arguments. But what this cookie-cutter sameness means is that clever variations can sometimes prove decisive.

The cutting edge of cleverness can be glimpsed in West Palm Beach, Fla. There, Richard Pinsky, a former campaign operative for Pat Robertson and Bob Dole, works as a political detective. His job: to locate and bring into the lobbying fold what are known in the trade as "once close tos." On assignment from lobbying firms based in Washington, Pinsky is paid to find key individuals who were once close to lawmakers who are undecided on the legislation of the moment. He then ferrets out which of these confidants are willing to make the case to Sen. X or Rep. Y. In the argot of the multi-billion-dollar influence industry, Pinsky is doing grasstops--as opposed to grassroots--lobbying, since he avoids hoi polloi and zeroes in on those few people whom lawmakers know and whose opinions they trust.

When Pinsky was hired recently by the Dewey Square Group, a public relations and political consulting firm, to rally support for "fast track" legislation, he called an old ally, former Republican Gov. Bob Martinez. Martinez, in turn, discussed the issue with fellow Tampa resident and Democratic Congressman Jim Davis. Davis, an impressionable freshman, is now a firm yes on the free-trade measure. Although Davis' spokesman insists the Martinez talk didn't affect the Congressman's vote, the little chat certainly didn't hurt. Nor did any of the casual-but-premeditated contacts made on fast track by another Pinsky recruit, former Florida Secretary of Commerce Charles Dusseau; he wrote to Congresspersons and fellow Democrats Corrine Brown, Peter Deutsch, and Robert Wexler.

The beauty of this tactic is that the lawmakers rarely know they've been lobbied. That's why it works so well. According to the FORTUNE survey, the most effective lobbying approach is the least overt: the simple presentation of accurate information, preferably by folks back home. As a result, the grasstops approach exemplified by Pinsky is spreading rapidly. Dewey Square is just one of several firms, such as Direct Impact and Lunde & Burger, that now maintain nationwide networks of politically wired operatives who are willing to reach for their Rolodexes in between their election-year gigs to help make ends meet. Campaign professionals like Susan Swecker of Virginia, Ken Benson of Texas, and Tylynn Gordon of Montana are becoming the new breed of influence peddlers. Yet they don't need to register as lobbyists in Washington. They don't even set foot in the city they affect so deeply.

Another innovation on an old lobbying theme is the Christian Coalition's automated telephone bank, which it calls Hypotenuse. Executive director Randy Tate records a request to his membership, usually about the need to pass or defeat legislation. Hypotenuse then sends the audio message, along with a digitized call sheet, via modem to personal computers around the nation. Those PCs, in turn, dial the preselected coalition leaders, deliver Tate's message, and thus spawn a wave of letter writing and phone calling from thousands of people who have already been trained in political action. Hypotenuse is faster than the older and slower boiler-room-style operations of the coalition's rivals. Its disadvantage is its similarity to the disfavored AstroTurf mass-response efforts. Any rush of pressure will always appear less than heartfelt no matter what instigates it.

Republican consultant John Grotta thinks he has a solution to the AstroTurf problem. He's marketing a customized telephone card that allows interest group members to call an 800 number, which connects them to politicians' offices that are chosen in advance based on the needs of the group and the caller's district and state. Unlike most mass-response plans, calls are made over a longer period by people who are personally motivated--and not compelled--to make them. In addition, the system keeps track of the lawmakers who have been begged and can detect which of the members really like to do the begging--for future reference.

The latest rage in lobbying is the Internet. Jack "Bombs Away" Bonner, whose Bonner & Associates has been a leader in call-'em-up-and-patch-'em-through tactics, has opened a new subsidiary, called NetRoots, dedicated to creating Websites for lobbying campaigns. NetRoots' site on global warming, paid for by companies that oppose President Clinton's mandatory cutbacks in carbon emissions, provides predrafted E-mails from farmers, senior citizens, and small-business owners that read as if they were self-composed and can be launched directly to congressional representatives with the click of a mouse.

Modern lobbyists, knowingly or unknowingly, are playing variations on a tune composed at least half a century ago. In the 1930s a 19-year-old Western Union messenger from Warren, Pa., Elmer Danielson, was paid 3 cents for every telegram he was able to send to Congressmen that expressed opposition to the Wheeler-Rayburn bill, a reform measure meant to stem the power of public-utility holding companies.

Danielson didn't prevail, and the most muscular lobbies of today don't always win either. For example, after years of struggle, underfunded Handgun Control Inc. finally defeated the fearsome National Rifle Association when Congress passed the Brady bill, which mandated a waiting period before handguns could be purchased. Moreover, the biggest bulls on the Power 25 are forever trying to gore one another, which often leads to standoffs and compromises. On topics ranging from free trade to the minimum wage, the AFL-CIO is locked in perpetual battle with the Chamber of Commerce of the U.S.A. (No. 15), the National Association of Manufacturers (No. 13), and the National Federation of Independent Business (No. 4). Other things being equal, the groups atop the list should be able to vanquish those at the bottom every time. But things are never equal.

It probably won't be long before the Internet is seen as just another Elmer Danielson stunt too. After all, lobbying is artifice, and the most tried and true methods eventually are found out and then flounder. The FORTUNE poll indicates that's already happening with one of the hottest new gimmicks of recent years: advertising. Ever since Harry and Louise killed Clinton's health-care plan in 1994, millions of dollars have poured into TV, radio, and newspaper ads from both sides of virtually every major policy debate. The technique has flourished because it's easy to see and therefore easy to sell to the home office.

It may be too easy. A slight 5% of respondents said they thought buying ads was one of the most important ways an interest group can get its point across in the capital. That perception shows in the rankings: The Health Insurance Association of America, which rose to prominence by running the Harry and Louise spots, was out of the running for the Power 25. It ranked a relatively lackluster No. 30. Perhaps in reaction to this kind of development, FORTUNE has learned that the Chamber of Commerce of the U.S.A. is considering dumping its multimillion-dollar in-house television operation to spend more of its money on lobbying directly and from the grassroots. "The world of lobbying is dynamic and fickle," polltakers Mellman and McInturff say. One thing seems certain: Washington's Power 25 will surely change, as will its favorite tactics.