(FORTUNE Magazine) – WASHINGTON IS HYPERVENTILATING OVER GOP THREATS to exercise the dread "nuclear option," an arcane procedural device by which Senate Republicans say they can ban any filibuster of conservative judicial nominees. Democrats are right to be furious; what's the point of being a Senator, after all, if you can't pull a Mr. Smith and grind the gears of government to a nationally televised halt? But they're confused about which subject is worth shutting down the Senate for.

The filibuster we need has nothing to do with judges (important as they are). No, it's about President Bush's request for $82 billion more for Iraq--or to put it more precisely, it's about the cumulative $300 billion tab we're slipping to our kids for a war we've chosen to fight but not pay for, even as we've cut taxes for the best-off.

The reluctance of Democrats to force a showdown over these choices is apparently the lesson the party learned from John Kerry's campaign, when Kerry was branded a flip-flopper who famously voted for the (last) $87 billion before voting against it. But the proper lesson of that episode was not that Democrats shouldn't stand up to an indefensible fiscal policy--it was that Democrats shouldn't be witless and inarticulate when they stand up to an indefensible fiscal policy.

Flash back (if you can bear it) to the hapless Kerry campaign, and you'll see why. In his epic remark, Kerry was referring to his vote for an alternative plan to fund last year's $87 billion by repealing a small portion of Bush's tax cuts for the top. That wasn't a sellout of the troops; it was common sense. What kind of nation makes its children pay for its wars in order to lower taxes on the best-off? It's just wrong. Kerry should have been able to knock this one out of the park.

But odds are you don't even know that Kerry had his own plan. That's because Kerry and his savants decided that this sentence--"I voted for my plan to pay for our own wars today, not the President's plan to slip the bill to our kids in order to cut taxes on the top"--was too complex a thought to risk sharing with the American people.

This paralyzing fear persists. When I floated the idea of insisting that the nation pay for the new $82 billion instead of adding it to the deficit, one senior Democratic Senate staffer grew quiet. "We don't want to get caught in the Kerry trap," he said. Translation: "Our megaphone is puny. We'll only be trounced by Karl Rove as unpatriotic. Uncle."

Well, buck up, Democrats. The country needs this debate; no other issue comes close. If you're the minority party, and if you're a little creative (a big "if" with today's Democrats), a filibuster is one of the few things that can give you power--or at least a real megaphone.

So what do Democrats want to use it for? To prove their devotion to Roe v. Wade--a "strategy" that guarantees a perception that Democrats care more about the right to an abortion than anything else in public life. It's heresy, I know, for a liberal to suggest that blocking GOP judicial nominations may not be the main reason God put Democrats on earth. But the opportunity cost is huge: When Democrats throw all they have at issues like abortion, they're not fighting for economic justice and fiscal responsibility, issues that could win them broad support if only ordinary people knew there was a party that cared for such things. And just think of the crossover appeal of a fund-the-war-today filibuster. After all, attacking fiscal immorality is just another way of protecting the unborn!

A pull-out-the-stops, read-from-the-Bible, Frank Capra--style teach-in on who's paying for Iraq while fortunate Americans (like me, and perhaps you) have their taxes cut could bring an end to our fiscal bender. Delivering this wake-up call when the Senate takes up the war bill in April is a priceless chance for 2008 prospects like Hillary Clinton or Joe Biden, but they're probably too busy burnishing their "strong on defense" credentials to risk it.

Barack Obama, this is your filibuster. It's the perfect sequel to your bipartisan, "beyond red and blue" debut at the Democratic convention last summer. A nation that's been sleepwalking when it comes to the injustice of its budget needs to hear why the choices we've made don't live up to our ideals.

MATT MILLER (www.mattmilleronline.com) is a senior fellow at the Center for American Progress and author of The Two Percent Solution: Fixing America's Problems in Ways Liberals and Conservatives Can Love.