Rep. Beto O'Rourke admitted Thursday that he went "too far" in Tuesday's Texas Senate debate by calling Sen. Ted Cruz "Lyin' Ted" and leveling attacks against the Republican incumbent.

When pressed during a CNN town hall Thursday night why he went on the attack despite repeatedly decrying the pettiness in politics, the Texas Democrat said that he didn't "feel totally comfortable" invoking President Trump's past nickname for Cruz. He said that he decided to bring up the name after Cruz started the debate with "another lie."

"I've got to tell you, it's something I don't feel totally comfortable with, and perhaps in the heat of the moment, I took a step too far," O'Rourke said. "I don't know that that's the way I want to be talking in this campaign."

"At the very outset when he began with another lie, I decided that I could either spend the rest of the debate responding to every single dishonest thing he said or I could make sure that everyone understood exactly what he's doing," O'Rourke said.

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

The Texas Democrat said that he did not plan to make the charge until the debate started.

"I was not," O'Rourke told Bash, who mentioned that Cruz said that his pollsters told him to go on the attack during the debate. "That's another lie," he said. "I don't have a pollster."

O'Rourke's comments came 24 hours after he told reporters in San Antonio that he did not want to go negative in the campaign. He also released three ads attacking Cruz the morning after the debate.

"I won't go negative. It won't be personal. I'm not going to be partisan. I'm not going to be petty. People are sick of that stuff. I'm sick of that stuff," O'Rourke said Monday night. "And if I'm going to walk the talk, this is my chance to do it in the remaining 22 days with everything on the line. We're not only going to run this the right way, but we're going to win this the right way."

Cruz labeled O'Rourke "desperate" over the barrage of attacks from Tuesday and Wednesday.