(Olivier Knox) Campaigning in the battleground state of Colorado, President Barack Obama warned women voters vital to his reelection effort that Mitt Romney would roll back their rights and had embraced "policies more suited to the 1950s than the 21st century."

Obama got a vocal assist from Sandra Fluke, who as a Georgetown law student advocated health insurance coverage of birth control—only to be branded a "slut" by conservative talk show icon Rush Limbaugh.

Fluke said she was "heartened" that "so many Americans…reached out to me and supported me, no matter what anyone's politics were." And she highlighted Obama's strong public support — before ripping into Romney.

"Mr. Romney could only say that those weren't the words he would have chosen," she said, drawing boos from the crowd. "Well, Mr. Romney, you're not going to be the candidate we choose. Because if Mr. Romney can't stand up to extreme voices in his own party, then we know he'll never stand up for us."

Fluke introduced Obama, who wasted no time in hammering home what he described as the high stakes of the 2012 campaign.

"The direction you choose when you walk into that voting booth three months from now will have a direct impact—not just on your lives but on the lives of your children and the lives of your grandchildren," he told a cheering crowd of supporters in Denver. "That's true for everybody, but it's especially true for the women in this country."

National polls have found a persistent gender gap: Obama does far better than Romney among women (notably single women), while Romney typically does better with men.

In Colorado, which both campaigns are targeting, Obama edges Romney 51 percent to 43 percent among women, according to a new Quinnipiac/NYT/CBS poll. Romney is up 56-39, that survey found.

Read More: Yahoo News