Gavin Newsom, the photogenic San Francisco mayor who recently dropped his hat into the California governor's race and then withdrew, expressed visceral frustration with President Barack Obama in an article published Wednesday.

The latest in a string of Obama critiques by gay rights advocates, Newsom's comments come on the eve of a remarkable upset by the Republican seeking to fill the Senate shoes of the late Sen. Ted Kennedy (D-MA).

"Oh, I can't get in trouble here," Newsom told New York Times columnist Maureen Dowd. "I want him to succeed. But I am very upset by what he's not done in terms of rights of gays and lesbians. I understand it tactically in a campaign, but at this point I don't know. There is some belief that he actually doesn't believe in same-sex marriage. But it's fundamentally inexcusable for a member of the Democratic party to stand on the principle that separate is now equal, but only on the basis of sexual orientation. We've always fought for the rights of minorities and against the whims of majorities."

The Obama-Newsrom rift apparently dates back several years. In 2004, the Senate campaign of then-Illinois legislature Barack Obama (D-IL) allegedly refused to have his picture taken with Newsom. At the time, Newsom was bathed in controversy after allowing gay couples to marry.

"I gave a fundraiser, at his (Obama's) request at the Waterfront restaurant," former San Francisco Mayor Willie Brown told the San Francisco Chronicle in 2008. "And he said to me, he would really appreciate it if he didn't get his photo taken with my mayor. He said he would really not like to have his picture taken with Gavin."

Openly gay Obama deputy campaign director Steve Hildebrand dismissed the account at the time, saying it was "a ridiculous story."

"Barack Obama gets his picture taken with gay people all the time," Hildebrand said. "Including me, his deputy campaign manager."

Newsom isn't gay. His staffers stood by the account. "He was pissed," one former staffer told the Chronicle.

Newsom also criticized Obama in general.

"[T]here's a growing discontent and lack of enthusiasm that I worry about," Newsom told Dowd. "He should just stand on principle, put this behind him and move on."

Speaking of his experience at the 2004 Democratic presidential convention, the San Francisco mayor noted that he became a pariah after his decision to allow gay couples to marry.

“There were five of us,” referring to the party's then-"shining stars." “A guy named Obama. I’m like ‘Why is he in here? This is ridiculous. I mean, he’s a state senator. I’m kind of insulted.’ Life was really good, and then it came crashing down. ‘You’re not going to be speaking at the convention. We overbooked.’ And then it becomes the house of cards with the Democrats excusing themselves from visits to this city and being in the same room with me."

Newsom's comments were noted early Wednesday by The Huffington Post's Sam Stein.