Still struggling for votes, Republicans conceded Thursday that the budget they plan to push through the Senate may fall short of President Bush's full $1.6 trillion, 10-year tax cut proposal.

GOP hopes for fully restoring Bush's plan began to fade after their effort to win support from maverick Sen. James Jeffords, R-Vt., seemed to flag. Jeffords' vote had been considered pivotal in the Republican effort to erase the blow that the Senate dealt Bush on Wednesday in voting to slice the tax reduction to $1.15 trillion.

"I've about run that string out," Senate Majority Leader Trent Lott, R-Miss., said of efforts to satisfy Jeffords. Jeffords has threatened to vote against Bush's budget because he says it would shortchange special education to make room for an oversized tax cut.

Jeffords did not rule out an eleventh-hour deal, saying, "I'm always open to suggestions." But Lott acknowledged that Jeffords' resistance meant the tax number may end up being below Bush's coveted $1.6 trillion figure.

"We're not in a bidding process. We're going to pass it. We're going to go to conference at whatever level the bill is at that time," Lott told reporters, referring to House-Senate bargaining on the final version of legislation.

On the floor of the evenly divided chamber, senators continued working through a $1.94 trillion fiscal blueprint for 2002 that would lay the groundwork for Bush's proposals for cutting taxes and restraining spending. A grueling series of nonstop votes on amendments began Thursday evening and was expected to resume Friday, with final passage likely Friday afternoon.

After a series of up-and-down votes, Republicans edged the tax cut number for 2002 through 2011 up to $1.2 trillion. Democrats pushed the size of a separate tax-cutting economic stimulus package the budget would allow for 2001 from $60 billion to $85 billion.

Bush won one expected victory when the Senate voted to shield tax legislation later this year from Democratic procedural delays, which would have forced Republicans to muster 60 votes for passage.

But Republicans were intent on pumping the tax number up further. Those involved said they were trying to lure several Democrats, including Sens. Ben Nelson of Nebraska, Max Cleland of Georgia and Robert Torricelli of New Jersey. Lott said Bush had begun talking to Democrats.

It was unclear, however, how much of the tax cut they might restore. In a Senate divided 50-50 between the two parties, Jeffords' defection would tip the balance toward Democrats because the only other senators likely to cross party lines are Sens. Lincoln Chafee, R-R.I., and Zell Miller, D-Ga.

"We checked with everybody and we're still holding," said Senate Minority Leader Tom Daschle, D-S.D.

In Georgia, Cleland was the target of radio ads by the state Republican Party tarring him for opposing some tax cuts in the past. Other ads by the Service Employees International Union urged both senators to vote against Bush's tax plan.

In remarks to a gathering of newspaper editors, Bush expressed little concern about Wednesday's setback to one of his chief domestic priorities, saying, "No one vote is decisive." And he renewed his argument that his proposed tax reduction would bolster the economy.

Bush urged the senators, when they cast the vote tomorrow, to remember that there are "a lot of people in our country who are beginning to hurt" from soaring energy bills and other costs.

But Bush did not mention the figure $1.6 trillion, a figure he has often called "just right" and has stuck by since making it a central plank in his campaign for the GOP presidential nomination in 1999.

Other Senate Republicans also seemed increasingly cautious about the prospects of restoring the tax cut's full size before Friday's final vote. "I'm hopeful we'll be successful here," said Sen. Phil Gramm, R-Texas, but he looked toward the House-Senate bargaining conference as an opportunity to restore the $1.6 trillion if need be.

"Whatever happens here, we go to conference, and every conferee will be in favor of $1.6 trillion," he said.

Congress' budget is a guide lawmakers refer to when they write tax and spending bills later, and does not need the president's signature. The House approved its version, including $1.6 trillion in tax cuts and other Bush priorities, last week.

Jeffords met Thursday morning with Vice President Dick Cheney and Lott in the ongoing effort to win him over. Afterward, Jeffords sent Cheney a note declining their latest offer.

A Lott aide asked a lobbyist for disabled people to try persuading Jeffords to vote for the budget, said one Senate Republican official, but that apparently produced nothing.

In other efforts to change Jeffords' mind, he was lobbied Thursday by Sen. Chuck Hagel, R-Neb., a co-sponsor with Jeffords of a bill aimed at boosting special education funds. And R.L. "Skip" Vallee, the Republican national committee member from Vermont, said he would fly to Washington Thursday night to meet with Jeffords.

Jeffords wants education for the mentally and physically disabled to be increased to $180 billion over the coming decade, compared to $6.3 billion this year. The White House was offering more than $150 billion.