It’s official: Senate Democrats will soon hold a vote on the Paycheck Fairness Act, which would update and strengthen the Equal Pay Act of 1963, a senior Democratic Senate aide confirms to me.

“This vote is going to happen,” the aide says.

The vote means this will likely be the next major battle in the war over women, and it could put Mitt Romney in a delicate political spot. It will force a choice: Either he supports the measure, which would put him at odds with the Senate GOP caucus (which voted against the bill two years ago), or he opposes it, which would put Romney at odds with his own rhetorical support for equal pay for women, potentially damaging him further among crucial female swing voters.

The looming vote could revive a recent controversy that erupted around equal pay issues. On a recent Romney campaign conference call, HuffPo’s Sam Stein asked Romney surrogates whether Romney supports the Lily Ledbetter Fair Pay Act of 2009, which mad e it easier for people to challenge pay discrimination. The campaign at first waffled, but then released a statement confirming that Romney “supports pay equity and is not looking to change current law.”

But Romney’s campaign has not said whether he would have signed that law in the first place.

Now Romney’s rhetorical support for pay equity faces another test in the looming Senate vote on the Paycheck Fairness Act.

This Act would put more pressure on employers to prove that differences in wages are not rooted in gender difference, and would make it easier for employees to divulge information about their salaries, which would in turn facilitate deterring or challenging pay discrimination.

Two years ago Senate Republicans opposed the Paycheck Fairness Act, which had strong support from Obama, and it’s likely they will do so again. But Romney is on record supporting “pay equity” in principle, so he’d either have to break with that principle, or break with Senate Republicans, at a time when the battle over the female vote is raging in the presidential race. If Romney supports the measure, it could make passage of it more likely.

“This is an issue that a number of women Democratic Senators are absolutely intent on addressing — they know that with women still being paid 77 cents to each male worker’s dollar, this is an issue of fundamental fairness that women across the country face daily,” a senior aide to a female Senator says. “A lot of women who don’t necessarily see this as a partisan issue will be watching.”

The Romney campaign, in its pitch for female voters, has argued that women don’t care about social issues as much as they do about jobs, and that pocketbook issues will ultimately drive the female vote. But the Paycheck Fairness Act is a gender issue that’s all about the pocketbook and the economy.