NEW YORK - There are many things that Rep. Anthony Weiner was never shy about, and one was telling people he hoped to become New York City's mayor.

But with a 2013 candidacy all but out of the picture for the embattled Democrat, and with Mayor Michael Bloomberg approaching the halfway mark of his third and final term, Weiner's Internet sex scandal has reshaped the political fight already simmering beneath the surface of New York City politics. It has even led a celebrity, "30 Rock" actor Alec Baldwin, to publicly toy with the idea of jumping in to the game.

Weiner "combined appeal to striving, middle-class people in the outer boroughs with the ideological left," many of them wealthier Manhattanites, said Hunter College political science professor Kenneth Sherrill. "That's a very hard combination to pull off."

More than half of city voters saying in a recent poll that Weiner shouldn't make a City Hall bid, leaving up for grabs the broad swath of votes that seemed destined for the Queens congressman.

A seven-term Democrat, Weiner acknowledged this week that he sent sexually explicit messages over Twitter to six women over the past three years and then lied about it. He got married last year; his wife is pregnant with the couple's first child.

Weiner announced Saturday he was entering professional treatment at an undisclosed location and requested a leave of absence from Congress amid pressure to resign.

Spokeswoman Risa Heller said in a statement that Weiner left home "to seek professional treatment to focus on becoming a better husband and healthier person. In light of that, he will request a short leave of absence from the House of Representatives so that he can get evaluated and map out a course of treatment to make himself well."

The statement did not say where he would receive treatment or what type was involved. A day earlier, Weiner acknowledged he had exchanged online messages with a 17-year-old girl in Delaware.

It's debatable who could most benefit from Weiner's downfall. Sherrill argues that one of those with the most to gain is Manhattan Borough President Scott Stringer, who runs the risk of fading into the background if the race becomes crowded with white male candidates. Now he could gain supporters from the ranks of Weiner fans who loved the congressman for his very public and very loud opposition to Republicans on national issues. Stringer, the professor said, can be similarly aggressive and authentic.

"You see him, you hear him, you say, 'That's a New Yorker,' as you do with Weiner," Sherrill said.

City Public Advocate Bill de Blasio and former city Comptroller Bill Thompson, the 2009 Democratic nominee for mayor, could also win support from those same progressives.

Many of Weiner's middle-class supporters living outside of Manhattan could shift to current Comptroller John Liu, a union ally who like Weiner is based in Queens, and who enjoys strong support among the Asian community there, Sherrill said.

De Blasio, too, is closely allied with the city's unions and lives in Brooklyn, where Weiner grew up and has many supporters. Meanwhile, City Council Speaker Christine Quinn's work on housing issues and her own middle-class background could also win her some of those outer-borough votes.

Weiner's scandal may have prompted one politician into action. Though Thompson had said he intended to run again, he long remained the only presumptive candidate who hadn't started fundraising. But on Friday, he formally registered with the city Campaign Finance Board as a mayoral candidate.

Thompson has some catching up to do. As of January, Weiner had raised $5.1 million, Quinn had raised $3.2 million and Stringer had raised $1.1 million. Liu and de Blasio trailed with $513,000 and $393,000, respectively.

"The money race is the key indicator now," said Baruch College politics professor Doug Muzzio, although he cautioned it is still very early and the race likely won't head into full swing until after the 2012 federal elections.