A divisive exchange between former HUD Secretary Julián Castro and former Vice President Joe Biden over healthcare on Thursday night has been one of the most talked about aspect's of the latest presidential debate.

Castro, who's struggled in the polls and is not at the top of the pack in the race for the Democratic nomination, did not hold back in his criticism of Biden on Thursday.

His ruthless attacks gained Castro's campaign a lot of attention, but Democratic strategists have suggested the move could backfire.

At the same time, one political scientist told Insider that Castro actually did Democrats a favor by addressing the elephant in the room, which is whether Biden is really up to the task of running for president.

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In the third Democratic presidential primary debate in Houston, Texas, former HUD Secretary Julián Castro accused former Vice President Joe Biden of forgetting the details of his own healthcare plan.

Castro's attacks on Biden led to widespread criticism from political pundits and some of his fellow 2020 candidates who felt he went overboard, but one political scientist told Insider he may have actually done Democrats a favor and unabashedly touched on a concern that needs to be addressed if they hope to defeat President Donald Trump.

Biden and Castro — both former Obama administration officials — support plans that would offer Americans a public option for health care in addition to private insurance.

Castro argued that while his health care plan would automatically enroll people who didn't have private insurance into a public option when they lost their jobs, for example, Biden's would require people to actively enroll, leaving some without coverage.

Read more: 'I'm fulfilling the legacy of Barack Obama and you're not': Julian Castro comes out swinging at Biden over healthcare in Democratic debate

"The difference between what I support and what you support is that you require them to opt in, and I do not require them to opt in," Castro said. "Barack Obama's vision was not to leave 10 million people uncovered — he wanted every single person in this country to be covered."

Biden argued that people would not have to buy in to Medicare under his plan, but Castro pushed back, saying, "You just said two minutes ago that people would have to buy in — are you forgetting already what you said two minutes ago?"

"I'm fulfilling the legacy of Barack Obama and you're not," Castro concluded, to which Biden retorted, "That'll be a surprise to him."

Castro was looking for a boost, but it could backfire

In attacking Biden, Castro was likely trying to get a polling bump for himself similar to the one that Sen. Kamala Harris received when she went after Biden on the issue of race in the first debate in June. Castro was fundraising off of his attacks on Biden not long after the debate ended.

"I had a critical choice to make on the debate stage last night," Castro said in an email to supporters. "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."

Castro has denied that he was attempting to raise questions about Biden's mental fitness by challenging the former vice president on if he could remember what he said "two minutes ago," but that's how it's been widely interpreted.

MSNBC's Chris Matthews described Castro's remarks as a "cheap shot" as CNN's Chris Cuomo suggested he went "too low" in that moment and asked if he regretted it.

There's an ongoing debate as to whether Castro was correct (PolitiFact rated his statement "Mostly False").

The transcript shows Biden at one point stating that his plan includes an option in which "you automatically can buy into this." This is what Castro was seizing on in the heated exchange, which he made clear in a subsequent tweet. Both campaigns have since claimed they were in the right.

After the debate, some of the other Democratic candidates criticized Castro's tactics. "I will disagree with Joe on our record and our vision for the future. I am not going to go after him personally, that's not right," Sen. Bernie Sanders told CNN.

But others, like Sen. Cory Booker, defended Castro.

"Look, 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," Booker said.

"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," he added.

Michael Gordon, a Democratic strategist and principal at a strategic communications firm Group Gordon, told Insider in a Friday phone interview he believed Castro's attack ultimately backfired.

Gordon said the attack "absolutely hurt Castro significantly more than it hurt Biden because of the nature of the attacks. They were more personal than policy-based and he just came across as angry rather than thoughtful...he needs to do something more original than simply attacking the front runner."

Gordon also suggested that while Castro's attacks backfired on him in the short term, they may have actually helped Biden's main rivals — Sens. Bernie Sanders and Elizabeth Warren, who had the benefit of Castro going after Biden on their behalf without being subject to the same amount of backlash.

'He did the Democratic party a service'

Stephen Nuño-Pérez, an associate professor and chair in the department of politics and international affairs at Northern Arizona University, also questioned whether it was politically prudent for Castro to go this route.

"I don't know if it was wise for him to do it," he told Insider on Friday, and it might hurt Castro down the line if he's vying to be on the ticket as a vice presidential candidate.

A FiveThirtyEight/Ipsos poll of Democratic primary voters confirmed Gordon and Nuño-Pérez's predictions, finding that Castro's net favorability decreased by 6.8% after the debate — the biggest drop of any candidate.

But despite the controversy and potential political consequences, Nuño-Pérez also said Castro did Democrats a huge favor.

"[Castro] did the Democratic party a service, because now the Democrats are talking about how Biden is continuously messing up. He's 76-years-old and this an issue the Democrats need to be honest about going into the election," he said.

Read more: Joe Biden responded to a debate question about slavery and reparations by going off on a tangent about how black parents should raise their kids, and people aren't happy about it

Nuño-Perez said that the Democrats are offering contradictory messages by saying 2020 is the "most important election in our lifetime" while simultaneously protecting someone (Biden) who they know is a "continual-gaffe machine," adding that Castro "pointed that out last night in a very direct way."

Echoing these sentiments, Preston Mitchum, an activist and adjunct law professor at Georgetown Law Center, told Insider, "People should have the right to actually talk about their concerns about Biden and his fitness to run for office without having complaints lodged against them that they're being ageist."

Mitchum, who identified as a Democrat, said the Democratic party is going to have a rough time in this election if the ageism defense is "all we have." The party has to take a hard look at what it wants, he said, and question whether someone like Biden is really the person who can go "toe-to-toe" with Trump.

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