Given the Senate's tenuous 50-50 partisan split, Bush administration officials and congressional Republicans seem increasingly convinced they will need votes from moderate Senate Democrats to shape next year's tax and spending plans more to the president's liking.

That support could be necessary because two moderate Republican senators — Lincoln Chafee of Rhode Island and James Jeffords of Vermont — continue to resist President Bush's push for a $1.6 trillion, 10-year tax cut and for less spending than they want.

Congress returns from its spring break this week, and GOP leaders hope to craft a House-Senate compromise budget for 2002 and push it through both chambers by May 4.

"What we'll have to do is a budget resolution that will have the support of a substantial number of Democrats," said Senate Budget Committee Chairman Pete Domenici, R-N.M.

Though lawmakers must still sign off, House and Senate GOP aides agreed last week to include a $1.4 trillion tax cut in a compromise budget, said one Republican, speaking on condition of anonymity. That is midway between the $1.2 trillion the Senate supported on April 6 and Bush's full proposal, which the more conservative House included in the budget it endorsed March 28.

The GOP aides also tentatively agreed to limit spending increases for many programs to less than 6 percent. The House supported Bush's plan to hold the increase to 4 percent. The Senate ignored him and voted for an increase of 8.3 percent.

Congress' budget is a guide that will be followed by binding tax and spending legislation.

A Republican drive to woo moderate Democrats would be a direct challenge to Senate Minority Leader Tom Daschle, D-S.D., who said he thinks he has the votes to minimize any increases to the Senate's $1.2 trillion tax reduction. Daschle has exceptional clout because the Senate is split 50-50 between the two parties and Sen. Zell Miller of Georgia is the only Democrat supporting the $1.6 trillion tax plan.

"I don't think they had the votes for $1.4 trillion when we left" for the recess, Daschle said in an interview. "And I don't think the votes have changed."

But if a group of Democrats supports substantially raising the tax figure and trimming spending, the payoff could be a budget triumph for Bush and a burnishing of his assertion that he is a unifier who can rise above Washington's partisan culture.

The Senate approved its budget by 65-35, with 15 Democrats joining all 50 Republicans in support. Days of lobbying by Vice President Dick Cheney, Senate Majority Leader Trent Lott, R-Miss., and others failed to yield enough votes to boost the chamber's $1.2 trillion tax reduction.

Two weeks later, many Republicans say they will need some of those 15 Democrats to pump the tax figure upward because of continued resistance by Chafee and Jeffords.

Those two signed a letter last week with moderate Democratic Sens. John Breaux of Louisiana and Ben Nelson of Nebraska saying the final tax figure should be "closer to $1.2 trillion." Some Republicans said that was encouraging because it showed the four are flexible, but others said Jeffords and Chafee seem too implacable.

As their price for a deeper tax cut, some Democrats say they want more debt reduction and agriculture spending. Eleven of the 15 Democrats who supported $1.2 trillion are from states Bush carried last year, enhancing GOP leverage over them, including Nelson, Breaux and Max Cleland of Georgia.

In at least 11 states, business, labor and other groups on both sides of the battle used Congress' two-week break to stage rallies, send supporters to senators' town meetings, and launch newspaper, radio and even some television ads.

"They're hammering me" with ads, said Nelson, who supported the $1.2 trillion in tax cuts and is a prime target in the GOP's bid to increase that number.

But Chafee and Jeffords, both from heavily Democratic states that Bush lost in last November's election, scoffed at the ad campaigns they faced.

"It's been the best reception I've ever had at home," Jeffords said of the recess.

Among the most biting ads were radio spots by the conservative Club for Growth in Rhode Island, Vermont, and Pennsylvania, home of GOP Sen. Arlen Specter.

One such ad accused Specter of "working to keep your taxes high." He, Chafee and Jeffords were the only three GOP senators who voted to trim the tax reduction to $1.2 trillion.

Many Republicans expect Specter to eventually support deepening the tax cut. But in interviews, Chafee and Jeffords continued insisting that Bush's tax proposal was excessive.

 Chafeesaid he opposed a $1.4 trillion reduction "at this stage" and that Republicans should first advance bills to buttress Social Security and Medicare.

Jeffords, who two weeks ago sought a 10-year, $180 billion commitment to special education, now cites a new demand: billions in new tax credits for health insurance for the poor and other programs.

"If I can spend it, it can be bigger," said Jeffords when asked if he would now support a deeper tax reduction.