Kentucky Gov. Andy Beshear (D) said Donald Trump needs to grow up when it comes to how he handles his political opponents.

Beshear compared the Republican presidential candidate to a middle schooler while speaking to CNN on Tuesday about the upcoming debate between vice presidential picks Minnesota Gov. Tim Walz (D) and Ohio Sen. JD Vance (R).

After watching clips of Trump calling Walz a “total moron,” the Kentucky Democrat said the American people deserve a leader who can make a point without defaulting to petty insults.

“What you just saw is a former president that shows he’s not presidential,” Beshear said. “I mean, think about that. That’s somebody running for president throwing out names like he’s in middle school.”

“We need a president that’s at least mature enough to be able to work with people on both sides of the aisle and not resort to calling somebody a name,” he continued.

Beshear advised Walz to stay above the fray and stick to the issues when he faces off against Trump’s running mate on Tuesday night.

“Tim doesn’t need to respond to people calling names,” he said. “He’s been a lunchroom monitor, he’s dealt with people who do that. He just needs to push forward with who he is, what he stands for and what this ticket stands for.”

Trump appeared to be on the defensive while talking about the upcoming Walz-Vance showdown during an interview on Fox Nation on Monday.

During the sit-down, he lobbed several insults at Walz while claiming that the CBS-hosted debate was already “rigged” in Democrats’ favor.

“[Vance is] going up against a moron. A total moron,” Trump stewed to former White House adviser Kellyanne Conway. “How [Kamala Harris] picked him is unbelievable. And I think it’s a big factor.”

“There’s something wrong with that guy. He’s sick,” the one-term president added. “There’s never been a time in our country when people wanted change so badly.”