Julián Castro digs in as some Democrats express unease with his questioning of Joe Biden's memory

HOUSTON — Julián Castro struck a nerve Thursday night — and he's not saying sorry.

In sharply questioning rival Joe Biden's memory, the Democratic presidential candidate from Texas brought to the fore simmering concerns about the 76-year-old former vice president's fitness for office. And while Castro has sought to keep the spotlight on the policy dispute that fueled the moment, he held firm Friday on the overall exchange.

The tense interrogation, which came during a health care exchange at the third primary debate here, divided other candidates, with at least one saying Castro raised a legitimate issue and two more expressing unease with the topic.

In the latter category was Castro's fellow Texan, Beto O'Rourke, who felt the wrath of Castro in the first debate and said Friday morning he "wasn't really excited by" how Castro handled Biden. In a CNN interview, O'Rourke equated Castro's questioning with the "pettiness, the name-calling, the small-ball politics" that O'Rourke said will not defeat President Donald Trump and unite the country.

"Look, if you've got a policy difference with Joe Biden, by all means, let's air it at the debate, but that kind of personal attack I don’t think is what we need right now and is insufficient to the challenges we face," O'Rourke said.

The blowup came as Castro criticized Biden's health care plan, saying it would fall short of the goal of universal coverage because it requires people to buy in. After Biden denied that, Castro let it rip.

"Are you forgetting what you said two minutes ago?" Castro asked, "Are you forgetting already what you said just two minutes ago? I mean, I can't believe that you said two minutes ago that they had to buy in, and now you're saying they don't have to buy in. You're forgetting that."

A short time earlier in the debate, Biden made a reference to certain people being able to buy in to his plan, but there seemed to be more nuance than Castro implied. Biden first said "anyone who can't afford it gets automatically enrolled in the Medicare-type option we have." He later said that if Americans lose their jobs and the insurance that comes with them, "you automatically can buy into this."

In the immediate aftermath of the debate, Biden's campaign suggested that Castro had not learned from the first two debates that taking "personal cheap shots" at Biden has not worked for other contenders. Castro disputed the notion it was a personal attack, seeking to emphasize the broader policy debate they were having.

Castro continued to stand his ground Friday morning in media appearances and a fundraising email that told supporters he was being "viciously attacked" for fighting for them in the debate.

"I had a critical choice to make on the debate stage last night," Castro wrote. "I could either play it safe and give Vice President Biden a free pass like everyone else. Or I could speak up, challenge the conversation, and demand answers for you and your family."

Later Friday, Castro's campaign swiftly and forcefully denied a report that one of its staffers had called Biden's team to apologize after the debate.

Biden's campaign sent its own email to supporters saying Castro "got it wrong" and that the primary "should be decided on who can deliver for the American people, not who can throw the lowest blows (we already have a President who does that)." Biden declined to go that far Friday afternoon while speaking with reporters outside Texas Southern University, where all he said about Castro is that he has "got his facts wrong."

Asked by a reporter if it was fair for his rivals to play the "age card," Biden said he was fine with it and quickly pivoted to a positive review of Thursday night.

"Last night was the closest we came to a debate, OK?" Biden said. "We actually had an open debate on health care, and I felt very good about the debate on health care. What I saw last night was fewer and fewer personal attacks. ... I'm getting more and more comfortable with the way the debates are moving."

The one candidate who offered some cover to Castro was U.S. Sen. Cory Booker of New Jersey.

"There's a lot of people concerned about Joe Biden's ability to carry the ball across the end line without fumbling," Booker told CNN shortly after the debate. "And I think Castro has some really legitimate concerns about, 'Can he be someone in a long, grueling campaign that can get the ball over the line?' and he has every right to call that out."

At the same time, Booker added, "I do think that tone and tenor is really important, that we can respect Vice President Biden and disagree with him."

The level of discomfort with Castro's aggressive tack was more palpable among other hopefuls. Another rival of the two men, Amy Klobuchar, told CNN she found Castro's interrogation "so personal and so unnecessary," suggesting it was "something that Donald Trump might tweet out."

Questions about Biden's mental acuity are not new in the primary, though Castro seemed to give voice to them in the biggest venue yet, intentionally or not. Asked if he would release his medical records to assuage any concerns about his health, Biden got punchy with a reporter Friday afternoon.

"What health concerns, man? You wanna wrestle?" Biden said before more seriously adding, "Before the first vote, I'll release my medical records. There's no reason for me not to release my medical records."

Disclosure: Texas Southern University has been a financial supporter of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune's journalism. Find a complete list of them here.