In the tug-of-war for women's votes, Republican presidential nominee Mitt Romney appears to be gaining some ground.

A new ABC News/Washington Post poll, conducted from May 23-27, shows female voters' support for Romney spiking a full 13 points this week, from 27 to 40 percent. President Barack Obama's favorability ratings fell from 58 to 51 percent in the same poll, further narrowing the gender gap between him and the GOP hopeful.

Most of Romney's gains, the poll finds, are among unmarried women -- a bloc of voters who have overwhelmingly registered their disapproval of Romney in polls conducted throughout the past several months.

"Whatever variations cropped up in this holiday weekend poll, the fact is that Mitt Romney has the lowest favorable rating of any candidate of either party at this point in the race, according to ABC's own polling," said a spokesperson for the Obama campaign.

The gender gap was a major factor in propelling Obama to victory over Sen. John McCain (R-Ariz.) in 2008, and both Romney and Obama have made very clear efforts over the past couple months to secure the women's vote for 2012. The Obama campaign rolled out the "Life of Julia" online tool, which walks users through an average woman's life and points out the various ways Obama's policies would benefit her more at every age than those supported by Romney.

Obama's team has slammed Romney on his desire to "get rid of" funding for Planned Parenthood and his failure to answer a question about whether he would have signed the Lilly Ledbetter Fair Pay Act.

Romney, meanwhile, has deployed his wife to court female voters and report back on what issues they care about. His campaign has also organized "Women for Romney" grassroots groups in several battleground states and started planning more events aimed at women, all the while arguing that female voters care more about the economy than they do about social issues like contraception.

While Obama still leads Romney in favorability among women, the new poll is the first evidence that Romney's efforts to reach female voters are beginning to resonate.

The Romney campaign did not immediately respond to a request for comment.