The Senate, sharply divided along party lines, voted for the first time last night to pump some taxpayers' money into congressional campaigns.

Voting on a Democratic-sponsored bill to overhaul Congress's widely discredited campaign financing laws, the Senate rejected, 49 to 46, a Republican effort to strip out public funding provisions designed to encourage compliance with voluntary spending limits.

For candidates who agree to the spending ceilings, the bill would provide government-paid "vouchers" for radio and television advertising worth 20 percent of a candidate's permissible level of campaign spending, or more than $20 million for Senate candidates alone.

It also would reduce mailing rates, offer direct funding for candidates who comply with limits but face opponents who do not, and assist candidates who face attacks from independent groups sympathetic to their opponents.

The Senate's action also reflects mounting public concern over special interest influences in campaigns, dramatized by the savings and loan scandals, and members' own frustrations over soaring campaign costs that keep them continually busy on a "money chase" for contributions.

Sen. Mitch McConnell (R-Ky.), who led the fight against the public funding provisions, estimated that the subsidies would cost more than $150 million per election cycle if the bill -- now limited to Senate contests -- is expanded to include House races.

Democrats last week dropped more far-reaching campaign financing provisions in hopes of fostering compromise. But last night's action marks the first vote by either house -- at least in recent years -- in support of using federal funds of any kind to help finance congressional campaigns. The only current federal election funding is the $1 income-tax checkoff box that helps fund presidential races.

The legislation, which came to the floor after three years of partisan stalemate, faces many more obstacles to final passage in both chambers. The House is scheduled later this week to consider two rival Democratic plans, one of which includes partial federal funding of congressional races.

If passed, the legislation faces a possible presidential veto. Before the vote, McConnell read a May 24 letter from President Bush saying he would veto the bill if it includes spending limits with public funding to enforce them.

In last night's vote, all Republicans voted to strip out the federal funding. Among Democrats, only Sens. Ernest F. Hollings (S.C.) and J. James Exon (Neb.) voted with the GOP.

The fight over federal funding, which constituted the major incentive for candidates' acceptance of spending limits, came as the Senate opened debate on campaign finance revision after three years of rancorous argument and inconclusive negotiations over spending ceilings.

With the failure of negotiations, Senate Democrats and Republicans agreed to fight it out, clause by clause, on the floor, with pledges across the aisle to avoid delaying tactics or preemptive strikes.

The Senate Democrats' bill calls for a variety of incentives to encourage candidates to comply with voluntary spending limits, which would range from $950,000 to $5 million, depending on state population.

Instead of spending limits, Senate Republicans are proposing to curtail only out-of-state contributions exceeding $250, with reduced mail and broadcast rates to encourage compliance with out-of-state spending "targets."

The two parties in the Senate came closer together late last week when the Democrats agreed with a Republican plan to bar all contributions from political action committees (PACs) in federal elections and to scale back their earlier proposal for broader public funding. But they remained divided on overall spending limits and the use of public funds.

In yesterday's debate, McConnell moved to strike the incentives involving taxpayer funding, describing the vouchers as a "veritable food stamp program for candidates."

Sen. David L. Boren (D-Okla.), chief sponsor of the Democratic bill, said spending limits and incentives to enforce them are necessary in order to "reduce the money chase that turns us into full-time fund-raisers and part-time United States senators."

Meanwhile, House Democratic leaders announced details of a campaign finance package that would permit congressional candidates to continue collecting as much as $275,000 per election from PACs, and Republicans denounced it as a "joke."

Under the Democratic plan, the House will have a choice between two approaches. One, developed by a leadership task force, would set a voluntary spending limit of $550,000 per election, with a 50 percent limit on PAC contributions and differing restrictions on PAC donations to candidates that favor large PACs, such as those run by organized labor. The second would set a 40 percent limit on PAC donations, provide up to $100,000 in public financing and reduce the maximum individual contribution from $1,000 to $500.

While House Speaker Thomas S. Foley (D-Wash.) called the Democratic proposals an "organized and effective way to bring reform to the campaign process," Republican Whip Newt Gingrich (Ga.) said Democrats have a "very clever bill which maximizes union power in Washington, D.C., and which maximizes incumbent survival."

Staff writer Tom Kenworthy contributed to this report.