Democratic presidential candidate Julián Castro on Friday defended his criticism of front-runner Joe Biden at the previous evening’s debate — saying he “wouldn't do it differently” and insisting the apparent questioning of the former vice president’s mental acuity “was not a personal attack.”

“This was about a disagreement over what the vice president said regarding health care policy,” Castro, a former secretary of Housing and Urban Development, told CNN.

“I pointed out this big difference in our approach and, no, Americans need to know that,” he said.

The heated exchange between the two former Obama administration officials, which came as Biden discussed his health care proposal, provided perhaps the most explosive moment of Thursday’s forum in Houston. Castro accused Biden of bungling his pitch, shouting at him from across the stage: "Are you forgetting what you said two minutes ago? Are you forgetting already what you said just two minutes ago?"

Kate Bedingfield, Biden’s deputy campaign manager and communications director, said Friday the broadside "went over like a lead balloon" in the debate hall at Texas Southern University, telling CNN that Castro "hasn't learned the lesson that attacking Joe Biden in incredibly personal terms is not the way to advance yourself" in public polling.

"I think it has generally been panned as being disrespectful and classless, and so, again, I think that was a mistake on Secretary Castro's part, to say the least," she added.

Castro asserted Friday that Biden “couldn't hear me in the auditorium,” and claimed he would have similarly challenged “any opponent on stage” — not just the septuagenarian former six-term senator.

"We're up there to debate, so I'm going to continue to point out the differences,” Castro said. “If we're not there to point out the differences to the American people about our policy — not our personalities, but our policy — then why are we there?”

But Bedingfield argued Castro's interjections were not meant to elucidate policy distinctions with Biden, and belied a more disparaging message. "I think the implication was very clear, and frankly, it was very disappointing," she said.

Symone Sanders, a senior adviser to Biden, slammed Castro on Friday for taking "personal and cheap and, frankly, factually incorrect shots" at her boss. She also warned the offensive could backfire, citing California Rep. Eric Swalwell and New York Sen. Kirsten Gillibrand as examples of candidates who targeted Biden on the debate stage before dropping out of the Democratic contest.

"I think if you look at the history of folks deploying these tactics in a debate, it hasn't bode well," Sanders told CNN.

Castro later Friday continued to stand by his line of attack, rejecting murmurs that the barb was pre-planned and dinging fact-checkers who called his attack inaccurate.

In an interview on MSNBC, Castro said that fact-checking sites that downplayed the differences in each man's policy "missed the bar completely."

Castro did not back down from the exact language he used, either, telling anchor Chuck Todd that "we're up there to debate and that's what I was doing."

Many pundits and national Democrats, including a handful of the party's White House hopefuls, have denounced Castro's verbal assault, charging that his comments constituted an ageist dig and were misrepresentative of Biden’s stance.

“You know, I wasn't really excited about that,” said Castro’s fellow Texan and former congressman Beto O’Rourke, who equated the taunts to “the pettiness, the name-calling, the small-ball politics” practiced by President Donald Trump.

“That will not defeat Donald Trump. That won't bring this deeply divided country back together again,” O’Rourke told CNN. “So, 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 that we face.”

Minnesota Sen. Amy Klobuchar also took issue with Castro’s remarks, assessing that “the stakes are just too high” in next year’s election for that type of bitter Democratic infighting.

And although Klobuchar noted that she sparred on the debate stage with Vermont Sen. Bernie Sanders, a colleague with whom she enjoys “a personal friendship,” Castro’s barbs directed at Biden “felt different to me when he was sort of mocking him and making fun of him,” she told CNN.

Sens. Cory Booker of New Jersey and Kamala Harris of California, the candidates who have issued some of the harshest critiques of Biden and his record on racial issues in previous debates, were more reluctant to rebuke Castro outright.

Booker even suggested Thursday night that Castro’s attack had some merit, as Democratic voters ponder whether the gaffe-prone Biden is up to the challenge of sustained battle with Trump.

“I think that we are at a tough point right now because there’s a lot of people who are concerned about Joe Biden's ability to carry the ball all the way across the end line without fumbling,” the former Stanford football player told CNN. “And I think that 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.”

Booker appeared to take a step back from that metaphor during another interview on the network Friday, clarifying that he was not evincing public doubts about Biden’s memory.

“I think that we all have challenges at times. I can't even remember what I had for dinner last night,” he said. “The reality is what I'm calling into question is who is the best person to unite this party to get it done, to get in the end zone, not just for Democrats but for America.”

Harris seemed dismissive when asked about the controversy Friday, telling CNN that "things get heated” on a debate stage.

She also declined to rule on whether the swipes by Castro were out of bounds: “I'm saying that the focus should be on what we need to do to prosecute the case against Donald Trump, and for me, that is the focus.”

Caitlin Oprysko contributed to this report.