SAN ANTONIO Rep. Beto O'Rourke, D-Texas, on Tuesday invoked President Trump's past attacks on Sen. Ted Cruz by calling him "Lyin' Ted," and saying Trump invented that nickname because Cruz lies.

“Sen. Cruz is not going to be honest with you," O'Rourke said when asked about climate change after Cruz answered a question on that topic in their Senate debate. "He’s dishonest. It’s why the president called him Lyin’ Ted, and it’s why the nickname stuck. Because it’s true.”

[Related: In last ditch effort, trailing O'Rourke goes on attack against 'dishonest' Cruz]

O'Rourke went on to hit his Republican opponent for being a climate denier. Cruz fired back at the Texas Democrat by saying he is simply listening to his consultants.

“It’s clear Congressman O’Rourke’s pollsters have told him to come out on the attack," Cruz said. "So if he wants to insult me and call me a liar, that’s fine. But John Adams famously said 'facts are stubborn things,'" noting that O'Rourke supports raising the tax on a barrel of oil by $10.

The president is slated to hold a rally to support Cruz in Houston on Monday despite their fraught history during the 2016 campaign. Cruz has been a top ally of the president since his election nearly two years ago.