FLINT, Mich.—Even though the Democratic nomination he seeks is now within Hillary Clinton’s grasp, Bernie Sanders signaled more clearly than ever Sunday night that he’s not going quietly.

Indeed, as the two candidates took the stage here in a city brought to the national spotlight by a deadly water crisis, Sanders had just clinched a victory in the Maine caucuses—his third win among four states that held nominating contests over the weekend.

Clinton still holds a commanding lead in the delegate count, having amassed victories in states with diverse electorates more reflective of the modern Democratic Party, and the deficit is becoming increasingly difficult for her opponent to overcome. But Sunday’s debate also underscored the impact Sanders has had on her second White House run—highlighting her vulnerabilities on issues such as Wall Street influence and money in politics, topics that figure to play a key role in the Midwestern primaries on the horizon.

“I am very glad,” the Vermont senator said of his rival’s pledge to go after companies moving jobs overseas, “that Secretary Clinton discovered religion on this issue, but it's a little bit too late.

When he said Clinton’s support of trade agreements such as NAFTA, made under her husband’s administration, proved “disastrous” and costs jobs in the Midwest, and that she reversed course on Trans-Pacific Partnership, the former secretary of state responded with a new line of attack. She hit Sanders for opposing legislation in 2009 to bail out the auto industry. “He voted against the money that ended up saving the auto industry. I think that is a pretty big difference,” Clinton said.

“If you are talking about the Wall Street bailout, where some of your friends destroyed this economy--” Sanders said. Clinton tried to interject but Sanders shot back: “Excuse me, I'm talking.”

"If everybody had voted the way he did, I believe the auto industry would have collapsed, taking 4 million jobs with it," Clinton continued.

Contests on the horizon in Midwestern working-class strongholds (Michigan on Tuesday and Illinois and Ohio on March 15) will further shape the trajectory of the race. Clinton leads the polls in those states, which have gone Democratic in recent presidential elections. The two will participate in another forum on Monday in Detroit, sponsored by Fox News. Clinton will campaign in Cleveland on Tuesday night.

Sanders, an independent who describes himself as a Democratic socialist, has faced headwinds of his own during this campaign, particularly when it comes to race, guns and other issues that have figured prominently in the primaries. Clinton has embraced President Obama’s legacy ever more tightly in each debate in the hopes of building on his coalition.

When asked by a Michigan voter whose daughter was shot in Kalamazoo about ways to curb gun violence, Clinton argued for legislation to hold gun manufacturers responsible, noting that Sanders opposes it. "I voted against giving them immunity, but I think we should very seriously move to repeal that and go back to making sure gun makers and sellers are like any other business," she said.

Sanders disagreed: "If you go to a gun store and you legally purchase a gun, and then, three days later, if you go out and start killing people, is the point of this lawsuit to hold the gun shop owner or the manufacturer of that gun liable? If they are selling a product to a person who buys it legally, what you're really talking about is ending gun manufacturing in America. I don't agree with that."

The two rivals appeared largely in harmony on addressing Flint’s water crisis—Clinton made news by joining Sanders in calling for Republican Gov. Rick Snyder to resign, or, as she also suggested, be recalled—and both presented themselves as longtime fighters for the disenfranchised. They both insisted that they would continue to be involved in the struggles of Flint and other communities where, as Clinton put it, “government at all levels” has let voters down, after the spotlight from the presidential campaign and the network cameras have dimmed.

But when the CNN moderators took audience questions about jobs and opportunities, Sanders found room to pounce.

"One of us has a super PAC. One of us has raised $15 million from Wall Street for that super PAC. One of us has given speeches on Wall Street for hundreds of thousands of dollars," he said. "If you get paid a couple hundred thousand dollars for a speech, it must be a great speech. I think we should release it and let the American people see what that transcript was."

Clinton repeated that she would release the transcripts if her rivals made public their own transcripts from paid speeches.

"Secretary Clinton wants everybody else to release it. Well, I'm your Democratic opponent, I release it, here it is. There ain't nothing!" Sanders said. "I don't give speeches to Wall Street for hundreds of thousands of dollars, you got it."

Throughout the debate, whether discussing the economy and jobs or energy and fracking, Sanders looked for ways to bring the conversation back to what he called "establishment" politics. "Secretary Clinton ... she has the support of all the governors—Democratic-- all the senators, all the congressmen. I don't. I am not part of that establishment. I plead guilty."

Still, the tenor and tone of the debate was largely civil, and by no means reminiscent of the Republican forums of late. The two candidates pride themselves on sparring over policy instead of personalities. The mention of Republicans didn't come until the end of the debate, however.

"We have our differences," Clinton said. "But compare the substance of this debate with what you saw on the Republican stage last week."

"We are, if elected president, going to invest a lot of money into mental health. And when you watch these Republican debates, you know why we need to invest in that," Sanders joked.

"I think that Donald Trump's bigotry, his bullying, his bluster, are not going to wear [so] well on the American people," Clinton said when asked how she would take on the GOP front-runner in the general election.

"I would love to run against Donald Trump," Sanders said, when asked the same question. "I think we are exciting working-class people, young people who are prepared to stand up and demand that we have a government that represents all of us."