Democratic vice presidential nominee Tim Kaine said Tuesday that Donald Trump “ran out of gas” at the first general election presidential debate Monday night.

In an interview with “CBS This Morning,” the Virginia senator said he spoke to his running mate Hillary Clinton about the debate a little while after it ended Monday at Hofstra University on Long Island.

“I told her I thought on demeanor, she absolutely dominated it in terms of looking presidential while Trump kind of got flustered and really kind of ran out of gas and I talked about the fact that she offered details and plans and he didn’t,” Kaine said.

Trump “left a lot of questions unanswered,” Kaine said, including on taxes and how the GOP nominee suggested that he has tried to avoid paying taxes to show how smart he was.

Kaine said Clinton’s best moment was her comeback after Trump attacked Clinton for having a weak stamina.

“And she said you go to 120 countries and you sit before a House committee for 11 hours and talk about stamina. and just the split screen, I was watching, that was toward the end of the debate and she was going strong and he was out of gas by that point and that was very obvious,” Kaine said.

Toward the end of the debate, Trump began complaining about negative ads Clinton’s campaign has run against him and he suggested that he was going to say something negative about Clinton and her family. Kaine said he had no idea what Trump was implying.

“There were some items at the end of the debate that were almost kind of like random, non-sequiturs that I had no idea what he was talking about toward the end,” he said.

Asked if Trump is a racist for promoting the birther issue, Kaine said, “I don’t know Donald Trump, I’ve never met him and so I’m not gonna make that comment about him. But I will tell you, absolutely, the claim that he perpetrated for five years that President Obama was not a U.S. citizen is an absolutely bigoted and racist lie.”