President Biden is responding to former President Donald Trump’s taunts by contrasting Vice President Kamala Harris’ track record as a prosecutor with his GOP rival’s status as a felon.

Mr. Biden, 81, stumbled out of the gate at his post-NATO summit press conference late Thursday by referring to Ms. Harris as “Vice President Trump,” even as he tries to quell concerns about his cognitive performance.

Mr. Trump, 78, was quick to rub salt in the wound on his social media platform.

“Crooked Joe begins his ‘Big Boy’ Press Conference with, ‘I wouldn’t have picked Vice President Trump to be vice president, though I think she was not qualified to be president.’ Great job, Joe!” Mr. Trump wrote on Truth Social.

Mr. Biden, who insists he won’t drop out of the race, tried to clean up the remark by mocking Mr. Trump from his account on X.

“By the way: Yes, I know the difference. One’s a prosecutor, and the other’s a felon,” Mr. Biden wrote next to a screenshot of Mr. Trump’s post.

Ms. Harris served as a district attorney early in her career and as California’s attorney general from 2011 to 2017.

The presidential rivals are trading playground gibes at a critical moment for Mr. Biden’s candidacy.

Some Democratic lawmakers have called on him to drop his reelection campaign after a disastrous debate performance on June 27 in Atlanta. They say Ms. Harris or a Democratic alternative should take over the ticket.

Mr. Biden insists he is running. He says he would like to “finish the job” by defeating Mr. Trump for a second time.

At the same time, Mr. Biden says Ms. Harris would be ready to fulfill the duties of the presidency on day one if she is called upon.

• Tom Howell Jr. can be reached at thowell@washingtontimes.com.