The Lilly Ledbetter Fair Pay Act would allow workers to sue a company within 180 days of receiving any paycheck that they believe has been diminished by discrimination.

It would overturn a Supreme Court decision last year that held that pay suits had to be filed within 180 days of the original discriminatory action, even if it went unnoticed for decades. In some jurisdictions, the statute of limitation is 300 days.

The case was based on a suit by Ledbetter, a 28-year veteran of a Goodyear tire plant in Gadsden, Alabama, who was paid less than male counterparts in a similar supervisory position.

In late April, the bill fell three votes short of the 60 required to end Senate debate and move to final action. The House approved the bill last year.

Opponents charge that the measure would effectively eliminate the statute of limitations on pay discrimination and force businesses to defend themselves against stale claims. The bill has drawn a veto threat from the White House.

Now advocates are vowing to find the support required to take the bill to a final up-or-down vote in the Senate, where it would almost certainly achieve a majority.

“We’re going to come roaring back,” said Sen. Barbara Mikulski, D-Maryland, at a sweltering Capitol Hill rally that included dozens of young women holding placards calling for pay equity. “You’ve got to be riled up. You’ve got to be revved up.”

The event featured Ledbetter and several congressional female leaders, including House Speaker Nancy Pelosi, D-California, and former presidential candidate Sen. Hillary Rodham Clinton, D-New York.

It’s unclear when or if the measure will be placed on the Senate calendar. Legislative days are dwindling. Congress will be out of session for almost all of August and may return for only a few weeks after Labor Day before adjourning for the year.

Advocates say the bill would bolster women and minorities in the workplace, where they often don’t realize they make less than white men because pay scales are secret. They assert that unfair compensation especially hurts low-income women who are the sole providers for their children.

“This is not just a women’s issue, this is a family issue,” Clinton said.

She asserted that the economic argument in favor of the Ledbetter bill is resonating with voters and forcing Republicans to offer an alternative measure rather than simply oppose Ledbetter.

“It is not as good or as thorough as what we’ve proposed,” Clinton said of the bill written by Sen. Kay Bailey Hutchison, R-Texas. “But it sends a signal that [Republicans] are feeling pressure.”

The Hutchison bill would start the clock on the statute of limitations on the date when the alleged victim “has, or should be expected to have, enough information to support a reasonable suspicion of such discrimination.”

The bill, which has eight GOP co-sponsors, is an attempt by Hutchison to negotiate with Democrats. Her spokesman says that the Senate was not given an opportunity to amend the original Ledbetter bill on the Senate floor or in committee.

“She is trying to be constructive,” said Hutchison spokesman Matt Mackowiak. “We want to have a seat at the table … and correct the injustice” of workplace discrimination.

But supporters of the Ledbetter bill say it addresses the core issue of unfair limitations on discrimination claims.

The Hutchison bill focuses on the process of determining who should have known what when, which can lead to endless “he said, she said” arguments, says Jocelyn Frye, general counsel at the National Partnership for Women & Families.

“A discovery rule is not a substitute for a paycheck rule that was in place before the Ledbetter decision,” Frye said.

But business groups continue to have concerns about the Ledbetter bill. WorldatWork, an HR organization that concentrates on total rewards, doesn’t take positions on legislation. But it is leery of the measure’s potential effect to ratchet up retirement costs.

“The [Ledbetter] bill is problematic because it could have an impact on pension payments,” said Cara Woodson Welch, director of public policy for WorldatWork.

While legislative details are addressed in Washington, supporters of the Ledbetter bill say the issue it raises has political momentum.

“For younger women, pay equity is a determining factor in terms of their vote,” said Lisa Maatz, director of public policy and government relations for the American Association of University Women.

—Mark Schoeff Jr.