Consider the contrast between two groups of Democrats, in Wisconsin and in the nation's capital.

Washington Democrats, including President Obama, have allowed conservative Republicans to dominate the budget debate so far. As long as the argument is over who will cut more from federal spending, conservatives win. Voters may think the GOP is going too far, but when it comes to dollar amounts, they know Republicans will always cut more.

In Wisconsin, by contrast, 14 Democrats in the state Senate defined the political argument on their own terms - and they are winning it.

By leaving Madison rather than providing a quorum to pass Gov. Scott Walker's assault on collective bargaining for public employees, the Wisconsin 14 took a big risk. Yet to the surprise of establishment politicians, voters have sided with the itinerant senators and the unions against a Republican governor who has been successfully portrayed as an inflexible ideologue. And in using questionable tactics to force the antiunion provision through the Senate on Wednesday, Republicans may win a procedural round but lose further ground in public opinion.

Here's the key to the Wisconsin battle: For the first time in a long time, blue-collar Republicans - once known as Reagan Democrats - have been encouraged to remember what they think is wrong with conservative ideology. Working-class voters, including many Republicans, want no part of Walker's war.

A nationwide Pew Research Center survey released last week, for example, showed Americans siding with the unions over Walker by a margin of 42 percent to 31 percent. Walker's 31 percent was well below the GOP's typical base vote because 17 percent of self-described Republicans picked the unions over their party's governor.

At my request, Pew broke the numbers down by education and income and, sure enough, Walker won support from fewer than half of Republicans in two overlapping groups: those with incomes under $50,000 and those who did not attend college. Walker's strongest support came from the wealthier and those with college educations, i.e., country club Republicans.

Republicans cannot afford to hemorrhage blue-collar voters. In a seminal article in the Weekly Standard six years ago, conservative writers Reihan Salam and Ross Douthat observed: "This is the Republican Party of today - an increasingly working-class party, dependent for its power on supermajorities of the white working-class vote, and a party whose constituents are surprisingly comfortable with bad-but-popular liberal ideas like raising the minimum wage, expanding clumsy environmental regulations, or hiking taxes on the wealthy to fund a health care entitlement."

Put aside that I favor the policies Douthat and Salam criticize. Their electoral point is dead on. In 2010, working-class whites gave Republicans a 30-point lead over Democrats in House races. That's why the Wisconsin fight is so dangerous to the conservative cause: Many working-class Republicans still have warm feelings toward unions, and Walker has contrived to remind them of this.

Which brings us to the Washington Democrats. Up to now, the only thing clear about the budget fight is that Democrats want to cut less from discretionary spending than Republicans do. Quietly, many Democrats acknowledge that they have been losing this argument.

Thus the importance of a speech on Wednesday by Sen. Charles E. Schumer, a New York Democrat, intended to "reset the debate." As Schumer noted, the current battle, focused on "one tiny portion of the budget," evades the real causes of long-term budget deficits.

Schumer dared to put new revenue on the table - including some tax increases that are popular among the sorts of blue-collar voters who are turning against Walker. Schumer, for example, spoke of Obama's proposal to end subsidies for oil and gas companies and for higher taxes on "millionaires and billionaires." Yes, closing the deficit will require more revenue over the long run. But right now, the debate with the House isn't focusing on revenue at all.

Schumer, who spoke at the Center for American Progress, also suggested cuts to agriculture subsidies and in unnecessary defense programs. He proposed changes in Medicare and Medicaid incentives that would save money, including reform of how both programs pay for prescription drugs. The broad debate Schumer called for would be a big improvement on the current petty argument, which he rightly described as "quicksand."

To this point, Washington Democrats have been too afraid and divided to engage compellingly on the fundamentals of what government is there to do and how the burdens of deficit reduction should be apportioned. Wisconsin Democrats have shown that the only way to win arguments is to take risks on behalf of what you believe. Are Washington Democrats prepared to learn this lesson?

ejdionne@washpost.com