DETROIT — “Go easy on me, kid,” Joe Biden said as he and Sen. Kamala Harris greeted one another on the debate stage Wednesday night.

She didn’t. Neither did he. In fact, the 10 Democratic presidential candidates held back little as they exchanged fire over immigration, health care, and who had committed the worst offenses when it came to criminal punishment and race relations.

Biden, the front-runner, was at the center of most exchanges, absorbing blows from all directions and delivering shots back, while the candidates spent relatively little time discussing the one figure who unifies Democrats, Republican President Donald Trump.

Biden needed to show a more steady presence after being blasted in the party’s first debate, and came armed this time to take on his rivals — unloading on Harris for engaging in “double talk” on her health plan, telling viewers to search for her record as a prosecutor, and attacking Sen. Cory Booker’s crime policies when he was mayor of Newark, N.J.

At times, though, it seemed like nine against one, as his rivals challenged Biden on his nearly five-decade record, and he found himself backtracking on or defending old comments and now-unpopular policies. "Everybody’s talking about how terrible I am on all these issues. Barack Obama knew exactly who I was,” Biden said of the man who selected him as his running mate.

Biden fumbled some of his lines, and seemed to lack a strong answer to criticism of the Obama administration’s deportation policies, but weathered the attacks much better than in the first debate, when he seemed stung.

Biden defends a more moderate health-care plan

Democratic voters consistently rate health care as one of the most important issues in the election, if not at the top of their agenda — and that was reflected over this debate and the one with 10 other candidates the night before, in which the arguments over how to expand health care, how fast, and whether to keep private insurance dominated long opening segments.

It’s a personal and emotional issue, and one that has animated Democrats for years. The Affordable Care Act is one of the party’s most significant achievements in a generation, and Democrats surged to control of the House last year largely on promises to defend the law.

But as this presidential campaign has shown, it’s also an evolving debate, one that has Democrats now pushing for more, especially after Sen. Bernie Sanders captured liberal imaginations with his Medicare for All plan.

Wednesday’s debate largely centered on Harris’ recently released health plan, which attempts to split the difference between those who want to eliminate private health insurance in favor of a government-run system and those who want to keep private plans but offer an option for people to buy into public health coverage.

Biden, who had been blistered by the Californian in the previous debate, blasted her plan’s cost ($3 trillion over 10 years, he said) and long rollout.

“Obamacare is working,” he said. “The way to build this and to get to it immediately is to build on Obamacare.”

He called for a public option built onto the existing law. Sen. Michael Bennet of Colorado joined in.

“It doesn’t make sense for us to take away insurance from half the people in this room and put huge taxes on nearly everyone in this room,” Bennet said.

Harris said her plan would cover all Americans and ensure “the kind of health care you get will not be a function of where you work.”

On immigration, Obama administration a double-edged sword for Biden

While Biden used Obamacare to defend his position on health care, his association with the Obama administration became more controversial when the conversation turned to immigration. He was asked several times — by moderators and rivals — to defend the three million deportations during Obama’s two terms.

Biden also defended his position that illegal border crossings should remain a crime instead of a civil offense, as proposed by former HUD Secretary Julian Castro. Biden noted that Castro was also part of the Obama administration.

“Mr. Vice President, it looks like one of us has learned the lessons of the past and one of us hasn’t,” Castro said to applause. “What we need are politicians that actually have some guts on this issue.”

“I have guts enough to say this plan doesn’t make sense," Biden shot back. “The fact of the matter is, when people cross the border illegally, it is illegal to do it unless they are seeking asylum. People should have to get in line.”

Through it all, Biden defended Obama as the president who protected the immigrants known as Dreamers through an executive order, rather than revealing anything about internal discussions about deportations or criticizing Obama.

“I was vice president. I am not the president. I keep my recommendations in private," he said.

Booker said Biden picks and chooses when to embrace Obama: “You invoke President Obama more than anyone in this campaign. You can’t do it when it’s convenient and not do it when it’s not.”

Later, Biden responded to a question about whether his ideas are progressive enough by citing the administration’s bailout of Michigan’s auto industry and helping Detroit get out of bankruptcy.

Booker takes his moment as candidates clash on crime, race

Booker arrived at the debate needing a breakout moment after months without gaining traction — and he and Biden had signaled that both were eager for a clash on criminal justice reform.

Biden opened by saying Booker “went out and hired Rudy Giuliani’s guy” as mayor of Newark.

“If you want to compare records, and frankly I’m shocked that you do,” Booker responded before lacing into Biden over his support for the 1994 crime bill, one he said the former vice president continued to promote until 2015. The bill had broad support at the time, but is now widely blamed for spiking incarceration, especially among people of color.

Several candidates blasted Trump as a racist, and the debate over criminal justice policy was one of the sharpest exchanges as the Democrats battled over who has done the most to help or hurt people of color.

African American voters have made up a key part of Biden’s support, and Booker and Harris, who are both black, have hoped to chip away at that advantage.

“There’s a saying in my community, you’re dipping into the Kool-Aid and you don’t even know the flavor,” Booker told Biden.

“I’m happy you evolved, but you offer no redemption to the people in prison right now” due to the law, he added. Booker balanced his attacks with calls for unity and earned positive reviews from pundits.

Harris and Biden then clashed again over Biden’s opposition to school busing in the 1970s. “It was wrong to take that position,” she said, returning to the topic that made her the star of the first debate last month.

But this time, Biden was ready and hit back, pointing to questions about Harris’ conduct as a state attorney general and misconduct by people she supervised.

“Google ‘1,000 prisoners freed by Kamala Harris,’” Biden told the audience of millions.

Not much splash for candidates who needed it

For lower-polling candidates, going after Biden was a strategy to inject oxygen into their campaigns. Only half of the candidates on the stage Wednesday have met the heightened requirements for the debates in September. And the evening seemed to do little to create moments that might improve the chances for seeing Bennet, Rep. Tulsi Gabbard of Hawaii, Washington Gov. Jay Inslee, and New York Mayor Bill de Blasio, and entrepreneur Andrew Yang next month.

Toward the end of the night, New York Sen. Kirsten Gillibrand, who’d hinted she’d be going after Biden, quoted an op-ed Biden wrote decades ago in which he said women working outside of the home were “avoiding responsibility," and would “lead to the deterioration of the family.”

Biden said the op-ed was written in the context of a child-care bill that he wanted to benefit lower-income families, rather than those earning a higher income.

“That was a long time ago," he said, noting that he wrote the Violence Against Women Act and that Gillibrand has commended him on his record on women’s rights. “I don’t know what’s happened except that you’re now running for president.”