By Alex Leary, Wall street Journal–

After months of distanced sniping, President Trump and former Vice President Joe Biden took to the debate stage for a 90-minute clash animated by fresh news developments and an enduring pandemic.

The first of three debates between the two candidates came days after a report alleging how little federal tax Mr. Trump has paid in recent years—which Mr. Biden quickly seized on—as well as the president’s decision to push ahead with filling a Supreme Court vacancy following the death of Justice Ruth Bader Ginsburg.

Mr. Trump arrived in Cleveland needing a jolt. He trails in national polls and in a number of key states as some voters are already casting ballots. Mr. Biden faced pressure to show he could withstand an unpredictable adversary and get across key points. Most people may be locked into their choice, polls show, but debates matter and millions watched.

Here are moments that stood out:

Things got rolling during a discussion about the Supreme Court that veered into a debate over health care, with the candidates repeatedly talking over each other. Both appeared initially comfortable in the setting, with Mr. Trump challenging questions from moderator Chris Wallace and Mr. Biden flashing a wide smile and laughing at some of the president’s responses. He repeatedly tried to directly address viewers, while Mr. Trump made slashing remarks, at times rattling the former vice president. He repeatedly reminded viewers that Mr. Biden has been in office for nearly five decades and questioned why he hadn’t accomplished more.

Things quickly spiraled into a rhetorical brawl.

Mr. Trump, 74, has long sought to brand his 77-year-old opponent as mentally and physically unfit for the job. More recently the Trump campaign sought to cast the former vice president as a seasoned campaigner, recognizing the risks of lowering the bar too far. Mr. Biden early on held his own, even as he stumbled over words and figures at times.

“I’m not going to listen to him,” he said at one point to Mr. Trump’s interjections. “Everything he is saying so far is simply a lie.” At another point, he said, “Will you shut up, man?”

Mr. Biden’s campaign went into the debate bracing for Mr. Trump’s anything-goes approach, which aimed to provoke anger or knock him off message. Mr. Trump for his part lashed out at Mr.  Biden as being a tool of the far left and noting his nearly 50 years in public office.

“There’s nothing smart about you,” Mr. Trump said.

“You’re the worst president America has ever had,” Mr. Biden later said.

And that was in the first 45 minutes.

Through it all, the coronavirus remains the defining issue of the race and it provided the sharpest contrasts during the debate.

Mr. Biden sought to portray the president’s handling of the coronavirus emergency as a deadly failure. All told, there are 7.15 confirmed infections in the U.S.—more than a fifth of the global tally—and more than 205,000 deaths.

“He panicked,” Mr. Biden said, looking directly into the camera as if talking to people at home. Overall, Mr. Biden sought to make the coronavirus a question of trust. “Do you believe for a moment what he’s telling you, in light of all the lies he has told you,” he asked.

The president countered with the steps he has taken, including restricting some travel and speeding along a vaccine.

“You would have lost far more people,” the president said. “He wants to shut down this country and I want to keep it open.” Mr. Trump was put on the defensive over mask wearing and holding rallies.

The economy remains one of Mr. Trump’s strengths, polls show, and he played to that, accusing his rival of trying to kill any progress that has been made. “People want their places open,” he said. “They want to get back to their lives.”

Mr. Biden briefly raised the issue of the moment—his rival’s tax records—but let it pass. Minutes later, though, Mr. Wallace raised the question. Pressed how much in federal taxes he pays, the president replied, “millions of dollars” without detail.

“Release your tax return,” Mr. Biden demanded.

Hours before the debate, Mr. Biden did just that, his 2019 tax return, showing he paid nearly $300,000 in federal taxes. The New York Times reported that the president paid $750 for 2016 and the same amount for 2017—and zero for years before that.

Mr. Biden has been trying to contrast his modest upbringing in Pennsylvania with Mr. Trump’s in New York, and during the debate he framed the election as “Scranton vs. Park Avenue,” an appeal to working class voters who helped elect Mr. Trump in 2016.

Mr. Trump has refused to release his returns, counter to decades of presidential precedence, saying he is under audit.

That morphed into a broader discussion about economic policy, giving Mr. Trump room to tout the gains that happened before the pandemic and accusing Messrs. Obama and Biden of presiding over a historically slow economic recovery. He accused Mr. Biden of being weak on China before pivoting to questions about the international business dealings of the former vice president’s son, Hunter. Mr. Biden strenuously defended his son.

Write to Alex Leary at alex.leary@wsj.com