This post has been updated to reflect President Obama's endorsement of Hillary Clinton.

President Obama endorsed Hillary Clinton Thursday afternoon after meeting with Bernie Sanders at the White House. But when he sat down with Jimmy Fallon on Wednesday for a "Tonight Show" interview airing Thursday night, he was still publicly neutral in the Democratic primary.

In clips released by NBC, you could tell Obama was itching to hit the trail — or, more accurately, to hit Donald Trump. The president offered Fallon a preview of his general election attacks on the presumptive Republican nominee.

"The role I'm going to be playing in this process is to remind the American people that this is a serious job," Obama said. "This is not reality TV."

Trump, in case you somehow forgot, starred on "The Apprentice" for 14 seasons.

Since he was staying neutral at that point, Obama was somewhat limited in what he could say about the Democratic candidates. Jabbing at Trump was probably the safest thing he could do.

But he might be on to something, if he plans to contrast his own seriousness — and the seriousness of the Oval Office — with Trump's fast-and-loose style. As Trump has brought his provocative brand of politics to the presidential campaign, Obama has seen his approval rating climb. He's currently at 50 percent, according to Gallup, with a net approval of plus-4 (46 percent disapprove of his job performance).

That isn't astronomical, but Obama has consistently been in positive territory since the start of primary voting. That's in contrast to the net-negative rating he carried for most of the previous 18 months.

It's hard to know how much Trump's rhetoric has contributed to Obama's recent surge. But the president is clearly in a better position to go after the GOP standard-bearer because his own public image has improved lately. Expect to see plenty of Obama making plenty of news, even in a campaign in which he's not on the ballot.