WASHINGTON — A bill that would pave the way for women to more easily litigate their way to pay equality failed to clear a procedural hurdle in the Senate on Tuesday as Republicans united against the measure for the second time in two years.

As Lilly M. Ledbetter, the woman whose name was attached to a 2009 law that ensured equal pay for women, watched from the gallery, the Senate voted, 52 to 47, to open debate on the legislation, 8 votes short of the 60 required.

“It’s a very sad day here in the United States Senate,” Senator Barbara Mikulski, Democrat of Maryland, said after the vote.

The bill would have built on the 2009 Ledbetter legislation, which adjusted the statute of limitations on equal pay lawsuits. Tuesday’s bill sought to bar companies from retaliating against workers who inquire about pay disparities and open pathways for female employees to sue for punitive damages in cases of paycheck discrimination. In 2010, the same bill failed a procedural vote in the Senate when no Republican supported it.