UPDATE 1-Pressure mounts on tweeting U.S. lawmaker to quit

* New Yorker calls Weiner 'very effective politician'

* Fellow House Democrat says he should go (Updates with member of House Democratic campaign committee saying he should resign)

By Thomas Ferraro and Daniel Trotta

WASHINGTON/NEW YORK, June 8 (Reuters) - U.S. Representative Anthony Weiner withstood calls from fellow Democrats and Republicans to resign on Wednesday as questions mounted if the fiery liberal can politically survive his online sex scandal.

"I think his hope and instinct is that he can stick it out," said a senior New York Democrat, asking not to be identified. "We'll see."

Allyson Schwartz, a member of the House of Representatives Democratic campaign committee, made it clear she had seen enough. "Having the respect of your constituents is fundamental for a member of Congress. In light of Anthony Weiner's offensive behavior ... he should resign," Schwartz said.

But Howard Witz, a real estate broker in Brooklyn, part of Weiner's district in New York City, said he would support Weiner again should he stay in politics.

"It's a shame because he's a very effective politician," Witz said. "Disappointed? Maybe. But does it make me quit on him? No it doesn't. As long as he didn't commit a crime."

Another New Yorker, Joe Mele, was blunter in talking about Weiner, who has voiced ambitions to run for mayor of New York in 2013.

"Mayor? I don't think he should be dogcatcher," Mele said.

Weiner, married to a longtime aide to Secretary of State Hillary Clinton, acknowledged on Monday he had inappropriate Internet and telephone conversations with six women. But the 46-year-old lawmaker said he had broken no law and would not resign. [ID:nN06169942]

Dan Ripp of Bradley Woods, a private firm that tracks Washington for investors, said he expected Weiner to quit within days.

"I think he's history," Ripp said. "Democrats aren't giving him the time of day. He has no clout. His own party is looking at him like a bozo. He is dragging them down."

MAYOR BALDWIN?

A little more than half of New York City voters think Weiner should remain in office, according to a NY1-Marist poll taken just hours after his tearful admission.

But a majority, 56 percent, say he should give up his hopes of becoming the next New York mayor.

Actor Alec Baldwin, long thought to be considering a political career, may jump into the race.

"I wouldn't rule it out," his publicist Matthew Hiltzik said, responding to a report in The Daily online publication, which reported that the star of television's "30 Rock" believed the Weiner scandal had improved his chances to become mayor.

House Democratic Leader Nancy Pelosi has asked the House Ethics Committee to investigate whether Weiner violated any of the chamber's rules.

House Republican Leader Eric Cantor on Tuesday became the first top U.S. lawmaker to say Weiner should step down, saying Congress was too busy with other matters to deal with Weiner's tweets.

Former Democratic Party Chairman Tim Kaine, now running for the Senate from Virginia, also called on Weiner to step down.

"Lying is unforgivable, public lying about something like this is unforgivable. He should resign," Kaine told a television station on Tuesday in Charlottesville, Virginia. (Additional reporting by Richard Chang and Richard Cowan; Editing by Xavier Briand and Peter Cooney)