DETROIT — When Democratic National Committee Chairman Tom Perez asked the audience gathered for the last night of the second Democratic presidential primary debate in Detroit whether they missed former President Barack Obama, many suspected it wouldn't be the last time Obama's name was evoked that evening.

Obama's two-term No. 2, Joe Biden, took the stage moments later and was repeatedly forced to defend his political record, eight years of which he amassed under the country's first African American president.

After being heckled by protesters over the Obama administration's deportation of about 3 million people, Biden was grilled by New York City Mayor Bill de Blasio over what he did to prevent the expulsions.

"I asked the vice president, point blank, if he used his power to stop those deportations," the mayor said. "If you want to be president of the United States, you need to be able to answer the tough questions. I guarantee you, if you’re debating Donald Trump, he’s not going to let you off the hook. So did you say those deportations were a good idea or did you go to the president and say this is a mistake, we shouldn’t do it? Which one.”

Biden replied that he was following Obama's lead.

“I was vice president. I’m not the president. I keep my recommendations in private. Unlike you, I expect you would go ahead and say whatever was said privately. That's not what I do," the former vice president said. "What I do say to you is, he moved to fundamentally change the system. That’s what he did. That’s what he did. But much more has to be done, much more has to be done. “

New Jersey Sen. Cory Booker didn't miss a beat.

“You can’t have it both ways," Booker told Biden. "You invoke President Obama more than anyone in this campaign. You can’t do it when it’s convenient and then dodge it when it’s not."

Earlier, Biden defended his former boss' signature legislative achievement: the Affordable Care Act.

"Obamacare is working. The way to build this and get to it immediately is to build on Obamacare. Take back all of the things that Trump took away, provide a public option," he said of providing universal healthcare to "a vast, vast, vast majority of Americans."

Feeling the pressure, the longtime senator for Delaware quoted the previous president, who has said choosing Biden as his running mate was "one of the best decisions he ever made."

"Everybody’s talking about how terrible I am on all these issues. Barack Obama knew exactly who I was," he said.

The abandonment of Obama is another example of how the 2020 Democratic presidential field has lurched to the Left.

"Who lost the #DemDebate2? @BarackObama," former Republican National Committee Chairman Michael Steele tweeted. "He got unnecessarily trashed by his own "team" on #Immigration, #Obamacare, #Deportations. These candidates do know they are running against @realDonaldTrump, right?"

Who lost the #DemDebate2? @BarackObama. He got unnecessarily trashed by his own "team" on #Immigration, #Obamacare, #Deportations.

These candidates do know they are running against @realDonaldTrump, right? — Michael Steele (@MichaelSteele) August 1, 2019

Republican-leaning Purple Strategy manager director Rory Cooper added that it sounded "like half these candidates wouldn't even invite President Obama to the convention."

Sounds like half these candidates wouldn't even invite President Obama to the convention. — Rory Cooper (@rorycooper) August 1, 2019

Eric Holder, an Obama administration attorney general, issued a solemn warning: "To my fellow Democrats. Be wary of attacking the Obama record. Build on it. Expand it. But there is little to be gained - for you or the party - by attacking a very successful and still popular Democratic President."

To my fellow Democrats. Be wary of attacking the Obama record. Build on it. Expand it. But there is little to be gained - for you or the party - by attacking a very successful and still popular Democratic President. — Eric Holder (@EricHolder) August 1, 2019

The tactic is not without risk for the White House hopefuls. When Obama left office in January 2017, he had an approval rating of 57%, according to Gallup polling that month.