Donald Trump and his wife Melania (R) arrive at the White House Correspondents' Association dinner in Washington on April 30. (JONATHAN ERNST/REUTERS)

Ten days ago, Donald Trump was on top of the world.

President Obama had released his long-form birth certificate. Trump, touting the “birther” controversy as he sought momentum for a possible run at the GOP presidential nomination, was in New Hampshire crowing about it. Cable television showed the two men in a split screen! Everything was coming together.

Until it wasn’t. Last Saturday, Trump — or, more accurately, Trump’s hair — was the primary punching bag (can you punch hair?) in speeches by Obama and comedian Seth Meyers at the annual White House Correspondents’ Dinner. (Trump, in keeping with his reputation, greeted the good-natured ribbing with a stone-faced stare.)

Then on Sunday night, his “Celebrity Apprentice” show on NBC was preempted by breaking news coverage followed by Obama at his most presidential — delivering a speech announcing that Osama bin Laden had been killed.

There was other evidence that the air had begun to go out of the Trump balloon. A new Washington Post-Pew poll showed that just one in 10 people think Obama wasn’t born in the United States, half the proportion who said the same just a month ago. And, in a new Quinnipiac University poll, 58 percent of people said they would “never” vote for Trump. (An equal number in the survey said they would never vote for former Alaska governor Sarah Palin.)

Trump, because of his outsize personality, will remain in the news as long as he continues to talk about running for president. Of late, he has sounded even more serious about a bid, telling Bloomberg News that “in my mind, I have already decided. . . . I am going to announce.”

But the events of the past week undercut the notion that Trump is a serious — or even a semi-serious — contender.

Donald Trump, for politically peaking before you ever got into the race, you had the worst week in Washington. Congrats, or something.

Have a suggestion for Worst Week in Washington? Email Chris Cillizza.

Can’t remember who won worst week most recently?

By Chris Cillizza