Hours after what the F.B.I. called a second attempted assassination of former President Donald J. Trump, Elon Musk wrote on his social media site — and then deleted — a post suggesting it was odd that nobody had tried to kill President Biden or Vice President Kamala Harris.

Mr. Musk said the post on X had been intended as a joke.

In response to a user who asked, “Why they want to kill Donald Trump?” Mr. Musk, who has endorsed the former president and comments frequently on the U.S. presidential campaign, wrote: “And no one is even trying to assassinate Biden/Kamala.” His post, which was captured by X users, included a thinking-face emoji.

Mr. Musk took down the post after it immediately drew outrage. X says he has more than 197 million followers on the platform, which he bought in 2022.

“Well, one lesson I’ve learned is that just because I say something to a group and they laugh doesn’t mean it’s going to be all that hilarious as a post on X,” he said in a follow-up post early Monday. “Turns out that jokes are WAY less funny if people don’t know the context and the delivery is plain text,” he wrote in another.

The White House condemned Mr. Musk’s post on Monday, calling it “irresponsible.”

Andrew Bates, a White House spokesman, reiterated statements by Mr. Biden and Ms. Harris saying there was no place for political violence in the United States. “Violence should only be condemned, never encouraged or joked about,” Mr. Bates said.

The Secret Service said on Sunday that it had fired on an armed man at Mr. Trump’s golf club in West Palm Beach, Fla., while the former president was playing. A suspect was later arrested. The incident followed one in July in which Mr. Trump was shot in the ear by a would-be assassin while he was holding a rally in Pennsylvania. The shooter was killed by law enforcement officers.

Mr. Musk, the world’s richest man, has established a reputation as an edgy plutocrat not bound by social conventions when it comes to expressing his opinions and broadcasting what is on his mind to his followers. His power and wealth have made him relatively impervious to criticism, and his bluntness has made him a hero to many on the right who oppose what they call political correctness.

Several of his recent posts about the election have drawn criticism. Last week, he amplified the bogus right-wing claims that immigrants were eating pets in Springfield, Ohio. And after the music superstar Taylor Swift said last week that she would vote for Ms. Harris, signing her endorsement “Childless Cat Lady” in a reference to comments by Mr. Trump’s running mate, Mr. Musk appeared to offer jokingly to impregnate Ms. Swift, writing: “Fine Taylor … you win … I will give you a child and guard your cats with my life.”