Legislation to revise the rules on class-action lawsuits was blocked last night in the Senate, apparently dooming the measure -- the last surviving plank in Republicans' agenda for altering the civil litigation system -- for the rest of the year.

With support from a dozen Democrats as well as nearly all Republicans, the bill had more than enough votes for passage. But the legislation collapsed when Democrats pushed for votes on amendments dealing with other issues and Majority Leader Bill Frist (R-Tenn.), overriding objections from business allies, responded by cutting off all amendments and scheduling a showdown vote.

As Democrats predicted, Frist lost. The largely party-line vote was 44 to 43, 16 votes short of the 60 needed to cut off delaying tactics and move toward final passage.

Before the vote, Frist told reporters that the bill is unlikely to be resurrected because so little time remains for legislative business in this election year. But some Democratic supporters of the measure said they will continue to push for its approval.

The House has approved a similar bill and several other litigation initiatives. But the Senate has rejected, blocked or stalled all that have come before it, including bills dealing with medical malpractice, liability for gun manufacturers and no-fault compensation for asbestos victims.

The class-action measure would require that most such multi-plaintiff lawsuits be filed in federal court, shifting them away from state courts, some of which have become famous for large settlements with big fees for the lawyers that filed the cases.

The battle over the proposal pitted business interests against trial lawyers and an array of consumer, civil rights and other interest groups.

Proponents argued that the legislation would end the practice of "forum shopping" for sympathetic courts and stop lawyers from gaming the system to win big fees while their clients receive little compensation. Opponents contended that it would limit access to the courts by victims with legitimate claims and delay justice because federal courts are already clogged with cases.

Although the bill had at least 62 declared supporters, the coalition fell apart when Frist offered to consider no more than one unrelated amendment: a proposal by Sen. Edward M. Kennedy (D-Mass.) to raise the minimum wage, which Republicans were prepared to counter with a less expansive plan.

Democratic supporters of the bill, such as Sen. Thomas R. Carper (Del.), warned that Frist's tactics would wind up dooming the measure. An angry Carper said last night that the Senate's handling of the bill reminded him of "a TV reality show on a dysfunctional family."

Virginia's senators voted to move ahead with the bill, while Maryland's senators voted to block it.