Senate Republicans killed legislation Wednesday aimed at removing limits on how long workers can wait before suing their employers for pay discrimination.

Democrats, speaking to key constituencies of women, minorities and swing voters this election year, said they weren't finished trying to pass the bill.

"Women of America: Put your lipstick on, square your shoulders, suit up" and get ready to fight, Sen. Barbara Mikulski, D-Md., said moments after the bill's opponents denied supporters the 60 votes needed to proceed to full debate and a vote on passage. "The revolution starts tonight."

Debate on the legislation, which was proposed in response to a Supreme Court decision last year, was steeped in election-year politics and shadowed by a White House veto threat.

The vote sparked dueling news conferences Wednesday in which leaders of both parties accused each other of playing politics with key voting blocs in a year when the presidency, every House seat and a third in the Senate are on the ballot.

Democratic presidential rivals Hillary Rodham Clinton and Barack Obama swung through Washington to speak from short, prepared statements in favor of the legislation. It was the first time in months that both candidates spoke on the Senate floor, an indication of the bill's importance to voters the two are fighting for in their ongoing battle for their party's nomination.

But Republicans were unified against it enough to muster 42 votes to supporters' 56 votes. The bill passed the House in July, 225-199.

Watching from the Senate visitors' gallery overhead was Lilly Ledbetter, the Alabama woman whose discrimination case was thrown out by the Supreme Court and for whom the legislation is named.

Republicans took aim at Democrats for delaying the vote on the measure until dinnertime for the benefit of the Democratic presidential contenders.

"To have the schedule of the Senate revolve around the schedule of the presidential candidates strikes me as particularly ridiculous," said Republican leader Mitch McConnell of Kentucky, convening a news conference earlier in the day in front of the door to the darkened Senate.

Democrats shot back that Republicans had no intention of allowing the pay legislation to proceed, nor, for that matter, a provision in other legislation expanding pension benefits for World War II veterans living in other countries.

The presumed Republican presidential nominee, Sen. John McCain, who was out campaigning and did not vote, said he opposed the measure.

"Won't vote yes, and won't vote no," Sen. Chuck Schumer, D-N.Y., told reporters. "They don't want to vote. ... They don't know what direction to go."

Ledbetter was a supervisor at the Goodyear Tire & Rubber Co.'s plant in Gadsden, Ala., who sued for pay discrimination just before retiring after a 19-year career there. By the time she retired, Ledbetter made $6,500 less than the lowest-paid male supervisor and claimed earlier decisions by her supervisors kept her from making more.

The Supreme Court voted 5-4 last May 29 to throw out her complaint, saying she had waited too long to sue. Under the justices' decision, which they said was based on the 1964 Civil Rights Act, an employee must sue within a 180-day deadline of a decision involving pay if the employee thinks it involved race, sex, religion or national origin.

That opens the door for corporations to discriminate, Democrats said. The legislation would restart the statute of limitations for pay discrimination lawsuits each time an employee gets a paycheck affected by sexism or racism.

The high court's ruling, said Sen. Edward Kennedy, D-Mass., leaves a "gaping loophole" in civil rights laws.

"Our legislation closes this loophole by making clear that as long as the discrimination continues, a worker's right to challenge it continues as well," he said.

In a statement, the White House said, "The bill far exceeds the stated purpose of undoing the court's decision," and could effectively waive the statute of limitations in such cases and burden courts with claims.

Sen. Johnny Isakson, R-Ga., said the legislation would allow people to file discrimination suits against employers for deeds decades old.

"If they're discriminated against, we need to make sure there is timely evidence so the prosecution can be thorough," Isakson said.

Besides trial lawyers, the bill could appeal to women and minority voters for whom pay equity will be a top issue on Election Day.

"It's not just the Democratic base, it's a lot of swing voters," said Schumer, who chairs the Senate Democrats' campaign committee.

The bill actually received 57 votes in favor, but Majority Leader Harry Reid, D-Nev., switched his vote under a procedural rule to allow him to call up the bill in the future.

Six Republicans joined Democrats in voting to advance the bill. They were Norm Coleman of Minnesota, Susan Collins of Maine, Gordon Smith of Oregon, Olympia Snowe of Maine, Arlen Specter of Pennsylvania and John Sununu of New Hampshire.