“I’m saying for the first time that Democrats are more likely to hold the Senate than not.”

That quote comes from veteran Democratic pollster Stan Greenberg on a conference call with reporters just now. On the call, Greenberg rolled out a new poll of 12 battleground states that contained a striking finding: Democrats have racked up an enormous lead among single women, doubling that lead since July.

Of course, this is a double-edged finding. While the lead itself might be good news for Democrats, since it suggests their messaging geared towards women might be having a persuasive effect, the problem is that this demographic tends to sit out midterms. And so this finding once again underscores just how much is riding on the Democrats’ voter mobilization efforts. But even here, Greenberg said his poll found reasons for optimism.

The poll — which was taken for the group Women’s Voices Women Vote — found that in these 12 battlegrounds, the generic ballot matchup has not really moved since July. Democrats trail Republicans by two points in these states, 45-47.

But among unmarried women, Democrats now lead Republicans by 22 points, 58-36 — up from an 11 point lead in July. And among the Rising American Electorate — single women, young voters, minorities — Democrats lead by 21 points, 56-35. (The 12 battlegrounds are AK, AR, CO, GA, IA, KY, LA, MI, MT, NH, NC, and WV.)

This is very pronounced in four specific Senate races — in which Greenberg did additional polling:

* In North Carolina, Kay Hagan leads Thom Tillis by 45-41 among likely voters. But among unmarried women, she leads by 34 points, 60-26.

* In Iowa, Bruce Braley trails Joni Ernst by a single point, 44-45. But among unmarried women, Braley leads by 43 points, 66-23.

* In Colorado, Mark Udall and Cory Gardner are locked in a tie, 45-45. But among unmarried women, Udall leads by 33 points, 64-31.

* In Georgia, Michelle Nunn trails David Perdue by five points, 41-46. But among unmarried women, Nunn leads by 34 points, 65-31.

So why does Greenberg think Dems might end up holding the Senate? On the call, he cited a number of findings from the poll that, he insisted, suggest the election may be trending towards Democrats. The poll finds that Obama’s approval on ISIS (46 percent) is five points higher than his overall approval (41), which Greenberg suggested was perhaps responsible for the poll’s finding that Republican disapproval of Obama has dropped by seven points (which could mean the GOP base isn’t quite as energized). Meanwhile, Greenberg argued the poll also finds Republicans are under-performing with seniors — they lead only by five, 49-44.

But perhaps the most interesting finding of all concerned the Affordable Care Act. While disapproval is still high in the battlegrounds, core Dem voter groups are now citing it as a leading reason to vote. For single women as a category unto themselves — and for the RAE, too — a candidate’s position on the health law is the second most important factor, behind the economy.

This, Greenberg suggested, may help explain another of the poll’s key findings: Democrats appear to be closing the “enthusiasm gap” with Republicans in the battlegrounds. The poll found that of those likely voters who say they are voting Democratic, 91 percent of them are almost certain to vote — while only slightly more, 93 percent, of those who are voting for Republicans say the same.

“The health care law has become much more important as a reason why people are voting for Democrats,” Greenberg said. “The threat of repeal appears to be giving unmarried women and minority voters a reason to vote.”

If true, this would turn the conventional wisdom on its head: That the health law is a big plus for Republicans because it is energizing core Republican voter groups without having a similar impact on Dem voters.

Now, you regulars know that I advocate following the polling averages closely, and right now, they still show Republicans marginally favored to take the Senate. The major models — such as FiveThirtyEight and The Upshot — also show Republicans favored. Until these show otherwise, I see no reason to conclude anything has changed. But Greenberg’s findings are worth thinking about, as a way to understand the true dimensions of the voter mobilization challenge Democrats face.

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UPDATE: Page Gardner, the president of Women’s Voices Women Vote Action Fund, adds:

“The Senate races are tightening, and Senate candidates can’t win without the votes of unmarried women. In our new poll, unmarried women, African Americans and Latinos all indicate they will vote for Democrats next month, with big gains for Democrat candidates since we last conducted this poll in July.”

UPDATE II: A quick caveat about the above findings. The numbers on the four individual Senate races are not really that useful, because the samples were too small and they were weighted to polling averages and intended for message testing. However, the broader findings in the dozen battlegrounds about single women and the Affordable Care Act remain relevant — which means the broader points in the post remain unchanged.

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.