CNN invited both candidates in the competitive Texas Senate race to appear at it town hall event from McAllen, Texas Thursday night. Only one of them decided to show up.

With incumbent Republican Sen. Ted Cruz out of the picture, Democratic challenger Beto O’Rourke was given a full hour to make his case to voters. And while O’Rourke has run an overwhelmingly positive campaign, there have been signs as they head into this final stretch that he is willing to go after Cruz, both personally and on the issues. In addition to a new round of attack ads, O’Rourke took an aggressive stance during their debate this week.

CNN’s moderator, Dana Bash, asked him Thursday why he decided to “take a page right out of President Trump’s playbook” and evoke the “Lyin’ Ted” nickname Trump bestowed upon Cruz during their 2016 presidential primary fight.

O’Rourke said that as he listened to Cruz “lie” about his record during their debate, he decided in the moment to tell viewers, “Look, he’s dishonest, it’s one of the reasons that he got tagged with this nickname and that nickname resonates because it’s true.”

“But I’ve got to tell you, it’s not something I feel totally comfortable with,” O’Rourke continued, sounding very unlike Trump. “And perhaps, in the heat of the moment I took a step too far.” Asked if he “regrets” the comment, O’Rourke stuttered a bit before saying, “I don’t know that that’s the way I want to be talking in this campaign.”

Earlier in the event, O’Rourke doubled down on his intention to push for the impeachment of President Trump in response to a question from a college student. After hedging a bit, the candidate said that while there “may be an open question as to whether the president, then the candidate, sought to collude with the Russian government in 2016, he believes the president’s behavior during his joint press conference with Vladimir Putin was "collusion in action." Similarly, he said when Trump asked Attorney General to end the Russia investigation on Twitter, that was “obstruction in action.”

“I would liken impeachment to an indictment,” O’Rourke added. “There is enough there to proceed with the trial for a full vetting of the facts and to make the best informed decision in the interests of this country and our future.”

“I do think there’s enough there for impeachment,” he said. “And if asked, I would vote on it.”