The Senate last night approved a Democratic bill to overhaul congressional campaign-financing laws after voting overwhelmingly to ban senators from accepting honoraria for personal use from special interest groups.

The legislation, reflecting the first major rewrite of campaign-financing laws since 1974, was approved 59 to 40 with the support of five Republicans after a GOP alternative was rejected by a straight party split of 55 to 44.

The measure, strongly opposed by most Republicans and threatened with a veto by President Bush, would use taxpayer funds for the first time in congressional campaigns as an incentive to encourage candidates to comply with a new system of voluntary spending limits.

Borrowing a proposal from the Republicans, the Democratic bill also would ban political action committees (PACs) from making any contributions in federal elections.

A variety of other controls would be imposed on the complex, loophole-ridden system of campaign financing in what Democrats described as an effort to curb soaring costs of campaigns and curtail special interest influence. Republicans, accusing the Democrats of writing a partisan bill after failure of weeks of negotiations to achieve a bipartisan compromise, said the bill was tailored more toward reelecting Democrats.

The House is expected to take up a different version of the legislation Friday. In light of conflicts between the two houses and the veto threat, odds are regarded as tilted against enactment of the measure before the 101st Congress adjourns this fall.

But Sen. Mitch McConnell (R-Ky.), floor manager for the GOP bill, which rejected spending limits in favor of curtailing large out-of-state and PAC contributions, held out some hope for compromise. "I think there is a reasonable chance, most likely next year, that we can come together," he said last night.

The only Democrat to vote against final passage was Sen. Ernest F. Hollings (S.C.). Only five Republicans voted for the measure: William S. Cohen (Maine), Dave Durenberger (Minn.), James M. Jeffords (Vt.), John McCain (Ariz.), and Larry Pressler (S.D.).

With elections only three months away, the Senate did not even consider raising its pay next year to levels approved earlier by the House as it voted to include the honoraria ban in the campaign-finance bill. This raised the prospect that senators could receive $23,000 less in annual compensation starting Jan. 1, when the honoraria ban would take effect.

The House voted to prohibit honoraria last year but coupled the ban with a pay raise to make up for the lost income. Senators are now allowed to retain for personal use about $27,000 a year in honoraria.

In a surprise move striking at the portfolios of the chamber's wealthiest members who are least reliant on honoraria, the Senate voted 51 to 49 to limit all outside income -- including income from investments -- to 15 percent of senatorial pay, or about $15,000 a year.

Multimillionaire members, such as Sens. John D. Rockefeller IV (D-W.Va.) and John Heinz (R-Pa.), who often vote in line with the interests of less affluent members, drew the line here. They voted almost to a man against the move by Sen. Daniel Patrick Moynihan (D-N.Y.) to broaden a proposed limit on earned income to include interest, dividends and other investment proceeds.

Only minutes after they had grimly voted to cut their total annual income, the non-millionaires reacted almost like sports fans as Moynihan, standing in the center aisle of the chamber and bidding for "one more vote, one more vote," finally succeeded in spreading the sacrifice more equitably through the chamber.

The honoraria ban, which would allow senators to continue collecting fees of $2,000 per appearance only if they give the proceeds to charity, was approved 77 to 23.

While prospects for final enactment of the campaign-finance measure are seen as dim, Sen. Christopher J. Dodd (D-Conn.), chief sponsor of the honoraria ban, said he will keep trying to attach the prohibition to legislation until it becomes law. Yesterday's roll call is expected to make it difficult for senators to reverse their votes.

During a brief debate in which no senator rose to challenge his argument about the propriety of honoraria, Dodd said the fees are nothing more than "influence-peddling schemes" with food and described his final honoraria appearance as "15 minutes . . . a cup of coffee and a Caesar salad for two grand."

Yesterday's vote came only a week after the Senate formally denounced Durenberger for using a book promotion deal to circumvent honoraria limits and reflected mounting concern within the chamber about ethical practices, many involving special interest groups, that have tarnished its image.

An eventual vote to ban honoraria became a near certainty last year when the Senate refused to go along with the House in banning honoraria and raising members' pay from $89,500 to $124,400 by the start of 1991. Instead, the Senate approved a modest cut in its honoraria limit and a proportionately modest pay increase to $101,400 by late this year.

At the time, many members said public pressure would force the Senate to outlaw honoraria and warned that it could wind up without a pay raise or honoraria. "A lot of members said to me we really blew it" last year, Dodd said after yesterday's vote.

While a vote to increase pay is considered unlikely before the elections, many senators expect such a move in a post-election session or early next year.

Reluctant to lose their honoraria but even more reluctant to go on record as trying to keep it, other senators tried to talk Dodd out of offering his proposal and were nowhere to be seen when he took the Senate floor yesterday morning.

His two cosponsors, Sens. Robert C. Byrd (D-W.Va.) and Terry Sanford (D-N.C.), eventually turned up, with Byrd, president pro tempore of the Senate and a former majority leader, warning bluntly that the reputation of the Senate was at stake.

"To my way of thinking, there is nothing honorable about honoraria," said Byrd, characterizing the payments as "an unethical practice that allows senators to give themselves a pay raise through the back channels of special interests."

Minority Leader Robert J. Dole (R-Kan.) spoke briefly in opposition to Dodd's proposal but only on grounds that it should be tied to a pay increase.

When the roll was called, Durenberger was one of the first to vote, and he voted for the proposal, as did the six members with cases before the Senate ethics committee.

Here are the key provisions of Democratic-sponsored legislation passed last night by the Senate to overhaul Senate campaign-financing laws:

Voluntary spending limits of $950,000 to $5 million, depending on state size, with incentives to encourage compliance that include taxpayer-financed broadcast subsidies amounting to 20 percent of the spending ceiling, reduced postal rates and standby funding in case an opponent exceeds the spending limit. The limits could be exceeded by 25 percent if the excess is in the form of in-state contributions of $100 or less. The limit on individual out-of-state contributions was reduced by a Republican proposal from $1,000 to $250.

Contributions from political action committees (PACs) would be banned for federal elections, with a standby provision to reduce the limit on individual PAC contributions from $5,000 to $1,000 and to impose aggregate limits on overall PAC gifts if the Supreme Court rules that a ban on contributions is unconstitutional.

Television advertising would get new rules, including reduced rates for candidates before an election, disclosure requirements for candidates who refuse to accept spending limits and opportunity for response to attack ads by independent groups.

"Soft money" not regulated by federal law would be barred from use by political parties in federal campaigns. Republicans failed to win approval of curbs on unregulated funds spent by labor unions and other groups on behalf of candidates in federal elections. "Bundling" of contributions to avoid legal limits on individual contributions would be banned.

Personal fund use by candidates who receive incentives for compliance with spending limits would be limited to $250,000; post-election contributions to pay off personal loans would be barred. Senators would be prohibited from sending out tax-financed, unsolicited mass mailings during years in which they are up for reelection.

Costs of the incentives for compliance with spending limits would be provided from postal funds and from voluntary contributions by taxpayers from their federal income tax refunds.