Joe Biden was asked to answer for Obama’s immigration record. He couldn’t.

Former Vice President Joe Biden struggled to defend President Barack Obama’s record on immigration during Thursday night’s Democratic debate when he was asked to respond to criticism of record-high deportations during his time as vice president.

It was a moment that illustrated that other Democrats see immigration as a weak spot for Biden — and that his ties to Obama can, at least on this issue, cut both ways.

Obama deported more than 3 million immigrants between 2009 and 2016, a record that drew persistent criticism from immigration advocates.

Moderator Jorge Ramos asked Biden, who’d been taking every opportunity to point out his close relationship with Obama, to defend that record: “[Y]ou served as vice president in an administration that deported 3 million people — the most ever in US history. Did you do anything to prevent those deportations?”

Biden said that Obama “did the best thing that was able to be done” and suggested that, as vice president, his own power was limited. He falsely claimed that the Obama administration “didn’t lock people in cages” and “didn’t separate families,” when in fact, it was done in limited cases.

He also pointed to Obama’s use of executive action to create the Deferred Action for Childhood Arrivals program, which has given legal status and work authorization to almost 800,000 young immigrants who arrived in the US as children.

Julian Castro accused Biden of dodging the question.

“I agree that Barack Obama is very different from Donald Trump,” he said. “He wants to take credit for Obama’s work but not have to answer any questions.”

But Biden did not budge, saying, “I stand with Barack Obama all eight years, good, bad and indifferent.”

Immigration has proven to be a weak point for Biden: He stumbled on the same question about whether he regretted Obama’s deportations at a Democratic debate in July, saying that he was vice president at the time and that he does not speak about his private recommendations to the president.

His opponents on the debate stage similarly accused him of selectively embracing parts of Obama’s record only when convenient.

But Castro said in July that it is “inevitable” that Biden will have to answer for Obama’s deportations at some point, and he tried to bring that moment about on stage in Houston.

Obama struggled to balance humanitarian concerns with border enforcement. As President Trump has repeatedly noted, it is true that Obama did separate families in immigration detention, albeit on a much smaller scale than the current administration.

Immigrant rights groups labeled him as the “deporter in chief” because he deported more immigrants than any other president — over 385,000 in fiscal years 2009 to 2011 and peaking at 409,849 in fiscal 2012.

And when facing his own migrant crisis in 2014, in which over 60,000 unaccompanied children from Central America showed up at the southern border, Obama initially responded by setting up temporary housing similar to the soft-sided facilities Trump has constructed and trying to detain migrant families for extended periods of time.

Former Obama officials have defended his record, saying the administration only targeted recent arrivals and violent criminals (although statistics showed that they also included parents of US citizens, among others). And particularly during and after 2014, Obama shifted toward more sweeping executive actions meant to protect immigrants who are already here.

Given Obama’s record and Biden’s reluctance to disavow it, immigration may well continue to be a thorn in the former vice president’s side and a sticking point for progressive voters.