Newsom, a charismatic, upand-coming politician often mentioned as a future candidate for much higher office, almost blew it all last week when he was forced to admit having an affair with Ruby Rippey-Tourk. Not only is Rippey-Tourk married to Alex Tourk - until now one of the mayor's best friends and his reelection campaign manager - at the time of the affair, she was also his appointments secretary.

So Newsom committed another cardinal sin of US public life by having sex with an employee.

This being San Francisco, however, the scandal has provided more amusement than moral outrage - although Tourk, for one, is no longer on speaking terms with the mayor and has resigned from his job.

Most seriously, it has raised questions about Newsom's political future. Ever since he split up with his glamorous wife, Fox News host Kimberly Guilfoyle, he has been seen consorting with a 19-year-old model (who may or may not have been drinking under age while out in public with him) and with Hollywood actress Sofia Milos from CSI:

Miami, who invited him to a Scientologist dinner party in Los Angeles. And the brief affair with Rippey-Tourk appears to have taken place while he was going through his divorce.

None of this is likely to dent his chances of re-election this year - a healthy majority of San Franciscans think he has done a good job. But Newsom is providing ever more fodder to heartland conservatives and talk-radio hosts who like to denounce 'San Francisco values' that, they say, are wrecking the nation's moral fibre. Even some of Newsom's fellow Democrats are furious with him for sanctioning gay marriage for a few brief months in 2004 - arguing that he triggered a national backlash against his party that allowed Bush to win a second term.

One of those Democrats, top consultant Jack Davis, said last week: "Gavin should resign and seek psychiatric help." Not that Davis is a paragon of virtue: a decade ago, he invited every luminary in town to a notorious 50th birthday party at which two strippers urinated on each other and performed unspeakable sexual acts with a Jack Daniel's whiskey bottle.