Anthony Weiner to Seek Professional Treatment, Requests Leave of Absence

"There were very few calls on Rangel to resign and he was censured of serious misconduct involving his office – really serious things that had potential for criminal charges," Sloan said. "We don't have anything remotely like that in the Weiner case."

Sloan explained that the mounting pressure on Weiner may stem in part from the early precedent set by House Speaker John Boehner when, at the first sign of sexual misconduct, he urged Reps. Mark Souder, R-Ind., and Chris Lee, R-N.Y., to resign, even though their behavior didn't appear to involve any abuse of their office.

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"A lot of people really hate Weiner, too," she said, referring to Weiner's colleagues in the House, some of whom are said to have been rankled by his personality and frequent media appearances.

As for Weiner's lies to his family, constituents and the general public in media appearances last week about the lewd photo that appeared on Twitter, Sloan said it was disconcerting and tarnished his credibility but is not the worst Washington has seen.

"A politician lying is not that unusual," Sloan said. "If the new standard is that politicians are out the second they lie to us, then a lot of politicians could be gone."

ABC News' Jonathan Karl contributed to this report.