A new poll found that women voters would choose President Obama over Mitt Romney by a two-to-one margin, giving Obama a critical advantage in contested battleground states.

The most recent USA Today/Gallup poll of voters in a dozen swing states found that six in ten women younger than 50 would vote for Obama, while about 30 percent would go to the Republican frontrunner. The two men were running even among male voters, with Romney boasting a slender one-point advantage.

As a result of Obama's disproportionate favor among female voters, the president registered a substantial lead over Romney in swing states. The poll has Obama easily defeating Romney in a hypothetical matchup, 51 to 42 percent. It was the first time in five USA Today/Gallup swing state polls that Obama scored a clear victory.

The poll surveyed potential voters in Nevada, Colorado, New Mexico, Iowa, Wisconsin, Michigan, Ohio, Pennsylvania, Florida, Virginia and North Carolina. Some of those states -- particularly Pennsylvania, Florida and Ohio -- are perennial swing states, while others like Colorado, North Carolina and Virginia have come into play more recently as shifting demographics have led the Obama campaign to focus on states that had been solidly Republican in past elections.

Women voters helped propel Obama to victory in 2008, choosing the president over Republican Sen. John McCain 56 to 43 percent. Recent polls have consistently shown the president tying his Republican rivals among men, but defeating them among women -- a late February Associated Press/Gfk poll gave Obama a 13 point margin over Romney -- a trend borne out by the USA Today/Gallup poll.

The new health care law championed by the Obama administration mandates that all employers -- including religious institutions -- provide health coverage for contraception. The rule unleashed a divisive debate over women's health issues, with Republicans claiming the mandate encroaches on religious freedom.

The issue seems to be damaging Republicans: the poll found that a majority of swing state voters follow the issue closely or very closely, and that voters were far more likely to disapprove of Rick Santorum or Mitt Romney's stances on government policy relating to birth control. Health care registered as the single most important issue for female voters.