Kamala Harris’ campaign taunts former President Donald Trump over his fixation with the sizes of his crowds in a new ad.

The 30-second clip — titled “Crowd Size” — cuts footage of former President Barack Obama mocking his predecessor over the obsession, during his address at last month’s Democratic National Convention, with video of Trump talking about his crowds and less-than-busy Trump campaign events.

Watch the ad here:

“Here is a 78-year-old billionaire who has not stopped whining about his problems since he rode down his golden escalator nine years ago,” Obama said at the DNC.

“There’s the childish nicknames, the crazy conspiracy theories, this weird obsession with crowd sizes,” Obama added, with a hand gesture that saw the audience erupt.

Watch Obama’s full DNC ding of Trump here:

Harris’ campaign released the ad on Tuesday, the day of what could be the first and only presidential debate between the vice president and Trump.

One of the first of tens of thousands of mistruths that Trump peddled during his presidency was about the size of the crowd at his inauguration in January 2021.

Trump recently also falsely claimed Harris had used artificial intelligence to make a crowd that attended one of her rallies appear larger in images.

“Trump spends a lot of time concerned about his crowd sizes, but the American people are far more concerned about which candidate will make their lives better – and it’s not the guy running on the Project 2025 agenda,” Harris campaign communications director Michael Tyler said in a statement sent to HuffPost.

Project 2025 is the right-wing Heritage Foundation’s playbook of extremist policies that Trump is widely expected to adopt if he wins back the White House, despite his attempts to distance himself from the plan that was authored by many of his former administration aides.

“Tonight’s debate will present the stark choice Americans will face at the ballot box: between Vice President Harris who is fighting for the people to make our lives better, and the guy who can’t seem to stop obsessing about himself and the size of his crowds,” Tyler added.

On Monday, Harris’ team shared this 60-second spot featuring comments from former Trump allies describing exactly why they’ve abandoned his pursuit of a potential second term: