Democratic pollster Stan Greenberg is not known for flinching from delivering bad news to Democratic politicians, and his new diagnosis of Obama’s slippage in the polls is no exception.

Greenberg told me in an interview that his new research persuaded him that Mitt Romney beat Obama in the debate for a simple reason. Unmarried women — a critical piece of Obama’s coalition — did not hear Obama telling him how they would make their lives better. By contrast, they did hear Romney telling them he’d improve their lives.

Greenberg says the research also indicates a clear route to winning reelection, however. “This is a major turning point and an opportunity for the president,” he says.

Greenberg did dial sessions among Colorado swing voters during the debate, and also conducted post-debate questionnaires. He found that unmarried women didn’t respond to Obama’s vow to improve the economy — which they found lacking in a clear overarching message.

“They heard nothing there that was relevant to them,” Greenberg says. “They were not hearing about issues or problems or things that Obama would do that affect their lives.”

Romney, however, succeeded in communicating with unmarried women, Greenberg says, by prefacing talk of his five point plan with an extended discussion of the economic strain of middle-income Americans — which Greenberg calls an effective “set up that gave his details meaning.”

“When Romney talked about what he is going to do for the middle class, his five point plan, they were very responsive,” Greenberg says. “The president had a lot of detail but didn’t have the set up in values.”

Unmarried women are a key piece of the “rising American electorate,” which includes young voters and minorities and propelled Obama's 2008 victory. “The key issues for them are the suite of economic issues around rebuilding the middle class,” Page Gardner, the president of Women’s Voices Women Vote, who commissioned Greenberg’s research, says. “They are the most stressed and stretched.”

Greenberg’s research also included a national survey, and focus groups in Ohio and Virginia, that suggest a course correction for Obama. The national survey found that before the debate, Obama was doing extremely well among unmarried women, beating Romney among them by 63-24. He held a 19 point edge among them on who would do better on “issues important to you.”

Greenberg says they were waiting for Obama to reinforce those perceptions — but he didn’t deliver. Greenberg believes that slippage among these voters is partly driving Romney’s gains. But he says Obama can still win them back, with a message fusing attacks on Romney’s comments about the “47 percent” with a passionate thematic contrasting Obama’s “we’re all in this together” values with Romney’s “you’re on your own” approach.

Indeed, Greenberg tested the following and found that 72 percent of unmarried women say it makes them more likely to support Obama:

When I look at our great challenges, I say, we’re all in this together. But the Republicans say, you are your own. Well that’s given us a country of just rich and poor and the well-connected using their power to get more tax cuts and breaks. Well, we need to make our country work for the middle class again. Clean up lobbyists and big money. Let’s keep taxes low for the middle class and small businesses and use the budget to help the middle class by seriously investing in education, rebuilding America, and making sure Medicare is there.

“The 47 percent critique is very important because it says Romney doesn’t understand their lives,” Greenberg concluded. By contrast, Obama needs to signal that he “understands what they are going through. They are looking for him to offer things that will impact their lives.”