WASHINGTON — Ka-ching!

President Obama is experiencing a fund-raising bonanza after announcing his support for gay marriage.

And he got a hero’s welcome on a West Coast swing that culminated last night in a star-studded Hollywood bash hosted by George Clooney.

“Thank You! Mr. President for standing up for my Mommys,” said a sign next to an infant who was outside a $17,900-per-plate fund-raiser near Seattle that hauled in $1.25 million.

Online contributions were pouring in, including a stunning $1 million in 90 minutes.

The Clooney soiree raised a stratospheric $15 million — more than half from online contributions in a raffle to win tickets to the event.

Guests sat at 14 round tables under a clear-topped tent on Clooney’s basketball court.

In the center, Tobey Maguire sat to the right of Clooney’s girlfriend, Stacy Kiebler.

Sitting near the pool was fashion guru Diane Von Furstenberg. Also joining the love-fest were Robert Downey Jr., Salma Hayek, Barbra Streisand and husband James Brolin, Jack Black and Billy Crystal.

“Obviously, yesterday we made some news,’’ Obama said. “But the truth is, it was a logical extension of what America is supposed to be.” Then he joked, “We raised a lot of money because everybody loves George. They like me, they love him.”

Studio mogul Jeffrey Katzenberg said, “Yesterday, he did the right thing yet again.”

The cash blitz came after Obama told ABC Wednesday that Vice President Joe Biden got “a little bit over his skis” with his own comments backing gay marriage Sunday, thereby forcing Obama to come out for it sooner than he wanted.

“Would I have preferred to have done this in my own way, in my own terms, without, I think, there being a lot of notice to everybody? Sure. But all’s well that ends well,” he said.

Obama acknowledged the political risks in swing states like North Carolina, where voters this week banned gay marriage.

“It would be hard to argue that somehow this is something that I’d be doing for political advantage because frankly, the politics, it’s not clear how they’re going to cut,” he told ABC.

GOPers hope Obama’s stance will motivate social conservatives to rally around Mitt Romney.

“Twenty-four hours ago, we were talking about what Romney had to do to get social conservatives on board,” said Ralph Reed, chairman of the conservative Faith & Freedom Coalition. “Now, they’re scrambling for a seat in first class.”

Romney sought to remind conservatives that his position had not changed, telling Fox News yesterday that marriage has been between a man and a women for “literally thousands of years” and shouldn’t be changed.