Former Attorney General Eric Holder on Wednesday urged 2020 Democrat candidates to pump the brakes on attacking the Obama administration’s record after some White House hopefuls took aim at former Vice President Joe Biden’s record.

“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,” Holder wrote on Twitter following the second and final night of the Democrat debates at the historic Fox Theater in Detriot, Michigan.

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 ideological divisions gripping the Democrat Party intensified on Wednesday as presidential candidates waged an acrimonious battle over health care, immigration, and race that tested the strength of early front-runner Biden’s candidacy.

The former vice president was repeatedly forced to defend his decades-old political record against pointed attacks from his younger, diverse rivals, who charged that Biden’s eight-year relationship with President Barack Obama was not reason enough to earn the Democrat nomination.

The attacks on Biden in the second presidential debate were most vivid coming from Sen. Kamala Harris (D-CA), who declared that his willingness to work with segregationists in the Senate during the 1970s could have had dramatic consequences on the surge of minority candidates in political office.

“Had those segregationists had their way, I would not be a member of the United States Senate, Cory Booker would not be a member of the United States Senate, and Barack Obama would not have been in a position to nominate” Biden to become vice president, she said.

When pressed, Biden repeatedly leaned on his relationship with Obama.

“We’re talking about things that occurred a long, long time ago,” Biden said. “Everybody’s talking about how terrible I am on these issues. Barack Obama knew who I was.”

The dynamic showcased the challenges ahead for Biden and his party as Democrats seek to rebuild the young and multiracial coalition that helped Obama win two presidential elections. Those differences were debated on a broad menu of issues including health care, immigration and women’s reproductive rights.

At one point in the debate, New York City Mayor Bill de Blasio pressed the former vice president on why he did not advise Obama to lessen the number of deportations during the administration. “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,’” de Blasio said. “Which one?”

“I was vice president. I am not the president,” Biden responded, placing the blame on his former boss.

That answer didn’t satisfy Sen. Cory Booker (D-NJ), prompting him to interject: “You invoke President Obama more than anybody in this campaign. You can’t do it when it’s convenient and then dodge it when it’s not.”

In an unexpected twist, Biden even found himself criticizing Obama’s record, including the Trans-Pacific Partnership (TPP) deal — an agreement President Trump ripped up — when pressed on whether he would sign the United States up for the Asian trade deal.

“I would not rejoin the TTP as it was initially put forward,” he said, botching the agreement’s acronym.

The former vice president also reaffirmed his disapproval of the U.S. troop surge in war-torn Afghanistan that occurred under the Obama administration in 2009.

“I opposed the surge in Afghanistan,” he said, before saying he believed a military intervention in Afghanistan was a grave foreign policy error.

After the debate, David Axelrod, former Obama political strategist and CNN senior political commentator, said that while Biden’s debate performance was an improvement from his first debate, it would be “bad news” if Wednesday’s effort was the best he could muster.

“I think the good news for Joe Biden is this was maybe the best he could do, and the bad news is this may be the best he could do. He was much better than last time. He was much more engaged,” Axelrod said. “But…he had moments in which he was uncertain, where he was on the defensive. And the main thing is, he was the guy who was going to take on Trump and bring it to Trump and restore values and decency.”

The Associated Press contributed to this report.