(FORTUNE Magazine) – Here's the political profile: A Westerner with an independent streak. A crusader against big money in politics. A brutal opponent of the tobacco industry. A loud critic of the GOP leadership for its hard line against gun control. A darling of the press corps.

Sounds like the description of the ideal Democratic presidential nominee. But Senator John McCain (R-Arizona) has a habit of turning up in uncomfortable places. As a Navy pilot, he was shot down over North Vietnam and logged time in the Hanoi Hilton, some of it in solitary confinement. Now he's the Republican candidate George W. Bush worries about most. He doesn't have the money of Steve Forbes, but he has something else: grit. Think of McCain as the candidate of True Grit: behind in the polls, behind in the money race, but ahead in toughness and ingenuity.

As a Senator, McCain believes in setting a bold agenda. He was the lone loud voice urging NATO to keep open the option of sending ground troops to Kosovo. He pushed to give President Clinton whatever authority he needed to prevail in the conflict. But he's also the one continually telling Trent Lott to allow campaign-finance reform to reach the floor. The best example of McCain going against the grain is this: He's the only candidate in a generation to travel to Iowa and oppose federal subsidies for ethanol, which is produced from Iowa corn. "It's always been in my nature, but when you've been where I've been, you learn to stand up for what you believe in--even if in the short run it may not look too smart," he says. "It doesn't get me voted Miss Congeniality in the Senate, but that's not what I'm running for. A lot of this stuff is a disgrace, and somebody has to speak up."

McCain turns up in the oddest places--trying to reform boxing, poking into the Olympics scandal, nosing around into how the government regulates the Internet. He's also turning up in New Hampshire. Former Senator Warren B. Rudman is squiring him around there, and a former executive director of the New Hampshire Republican Party is orchestrating his organization. He's considered strong in South Carolina, another early GOP test, especially since he's snagged the endorsement of two leading conservative Congressmen, Lindsey Graham and Mark Sanford. Their support suggests that McCain is acceptable to religious conservatives. Bush is ahead in both places, as he is everyplace. But right now the race isn't to become the Republican nominee but rather to be in a good spot if the Texas governor slips. McCain, who so often takes the differing point of view, is positioning himself as the GOP alternative.

DAVID SHRIBMAN is the Washington bureau chief of the Boston Globe and a Pulitzer Prize-winning political reporter.