You can’t keep a good Weiner down.

I believe it was F. Scott Fitzgerald who said there are no second acts in American lives, unless you’re a Twitter perv pitted against a field of charisma-less no-name losers.

Weiner leads [City Council Speaker Christine] Quinn 25 percent to 20 percent among registered Democrats, the poll by Marist found. That’s a flip-flop from the last survey in May, when Quinn, the longtime front-runner, led Weiner 24 percent to 19 percent.

Just as telling is the number of registered New York voters who said they might vote for Weiner. Forty-nine percent said they’d consider it, up from 40 percent two months ago, before Weiner entered the race. Those who said they wouldn’t consider voting for him dropped from 52 percent to 45 percent…

Weiner, meanwhile, saw his favorability rating among Democrats jump from 44 percent to 52 percent. His negative rating dropped from 44 percent to 36 percent…

Miringoff attributed the Weiner-Quinn reversal to the fact that Quinn, as the early front-runner, became the target of her rivals’ criticism as she tried to find the right balance of allegiance to — and independence from — outgoing mayor Michael Bloomberg. That drew some negative attention from Weiner.

This is good news, for two reasons. One: It’s good for blogging. The mayoral race will get much nastier now, with Quinn and the rest of the field in too much trouble not to rub Weiner’s face in Twittergate. Lots of easy content there, although I’m not sure it’ll hurt him at this point. Weiner’s whole strategy since he got in has been to eat shinola about his, er, peccadilloes when necessary but otherwise stick firmly to policy to show he’s a serious guy. The more Quinn tries to drag him into the mud, the easier it is for him to say that he’s the one candidate who’s interested in solving problems. The X factor is whether, as Weiner himself admits is possible, there’s more stuff out there from his Twitter fiasco that hasn’t been discovered yet. Maybe that won’t be a big deal. Maybe it will be.

Two: It’s going to make national Democrats sweat, especially Weiner’s mentor — and new GOP BFF — Chuck Schumer. Schumer’s been asked before about his candidacy and politely declined to comment. I wonder if that’ll change if Weiner’s lead starts to open, or if he’ll forever remain too skeevy for big-name Dems to buddy up with again. If Democratic leaders decide he’s too much of a liability to have back on a stage as big as Gracie Mansion, they’ll start helping Quinn in various ways — endorsements, donations, maybe a little oppo. The great fear for them is that he sneaks into the nomination with something like 41 percent of the vote among a crowded Democratic field and then his opponents’ supporters unite in disgust behind the Republican in the general election. Quinn is the safer choice as nominee, both in the general and as mayor. Time for national Democrats to answer the bell.

Exit question: Given that this poll basically confirms that any liberal with high name recognition can get a look from zero-standards New Yorkers, don’t you think Alec Baldwin regrets that he decided not to get in? Why should we have one boorish left-wing loudmouth who’s never passed legislation in the race when we could have two?