They are, by any reckoning, the most scorned people in politics -- moderate Republicans. For decades, going back at least to their rout at the Republican National Convention in 1964, they have been labeled as weaklings, folks who can't get organized and who never win. In other words, wimps.

Imagine Washington's astonishment, then, when a small band of moderate Republicans stood up to the leadership of Congress and to the White House and forced a major recasting of the budget just before the Easter recess.

On the House side, the moderates were able to lift the spending limits in the budget resolution enough to avoid severe cutbacks in Medicare and Medicaid and veterans' programs, while reducing the scale of President Bush's proposed tax cut from $726 billion to $550 billion.

In the Senate, moderates insisted the tax cut could be no larger than $350 billion, and by hanging tough in the final negotiations they won a personal pledge from the chairman of the Finance Committee that their demand would be met, no matter what.

On both sides of the Capitol, they showed they could -- for once -- exploit the close partisan balances and use their leverage to extract major concessions from the GOP's dominant conservative wing.

"At the end of the day," John Feehery, House Speaker Dennis Hastert's press secretary, told me, "they were able to dictate the outcome, because they had the votes. Their voice was heard."

Why were the moderates, who had been rolled so many times in the past, able to stand their ground this time? It turns out that without attracting much notice, they have been muscling up for just this kind of fight.

In 1997 Rep. Amo Houghton, a classic Eisenhower Republican and industrialist from Corning, N.Y., started something called the Republican Main Street Partnership to link the "Tuesday group" of House GOP moderates to outside contributors who prefer that kind of party.

Over the years, the group has expanded its fundraising capacity to the point where it could put $1.7 million into campaigns for like-minded challengers in 2002, and it has built a six-person staff under Sarah Chamberlain Resnick. This is tiny compared with the conservative apparatus in Washington (or the Democratic Leadership Council, on which Main Street has modeled itself) but a breakthrough for this wing of the party. A few weeks ago Resnick arranged for the first-ever breakfast meeting for several of its House leaders and like-minded senators -- among them Olympia Snowe of Maine, whose husband, former Maine governor John "Jock" McKernan Jr., is chairman of Main Street.

At the breakfast in the Senate Dining Room (right under the watchful eyes of Republican Majority Leader Bill Frist), Sens. George Voinovich of Ohio, Lincoln Chafee of Rhode Island, Arlen Specter of Pennsylvania and Snowe discussed the coming budget battle with Reps. Mike Castle of Delaware, Fred Upton of Michigan, Doug Ose of California and Houghton.

Specter soon opted out, but the other senators and most of the House moderates persisted. Eleven House Republicans signed a March 14 letter to Hastert and Budget Committee Chairman Jim Nussle saying they could not support the original Nussle budget. It was enough to force significant changes on the spending side. Then, on April 8, 15 House Republicans -- among them Rep. Tom Davis of Virginia, the former chairman of the House GOP's main campaign committee -- endorsed the $350 billion tax relief figure that Snowe and Voinovich were advocating.

The unusual coordination between the two sides of the Capitol produced benefits for both. Castle said the $350 billion limit set by Snowe and Voinovich "let us go to Denny [Hastert] and Nussle and say, 'You've got to agree on a reasonable figure.' " Snowe said, "The fact that I could point to a letter signed by 15 House members showed this was not an empty gesture."

Despite heavy White House pressure and predictions that the moderates would cave in, they won the day. The fight is not over, and there may well be retaliation. The anti-tax Club for Growth -- one of several groups on the conservative flank -- already is targeting Snowe and Voinovich with ads comparing them to France at the United Nations.

But the moderates have enjoyed a rare taste of victory. The Main Street membership list now includes 11 senators and 53 House members -- enough to make a difference on such issues as education, Medicaid and prescription drugs. As Mike Castle said, "The one thing they understand around here are votes. I think they know now we can take the pressure and not crumble."