Former President Donald Trump repeatedly delivered aggressive, often misleading attacks against a shaky President Joe Biden during a 90-minute debate Thursday night, offering millions of voters a stark contrast during a high-stakes rematch in which Biden’s performance was repeatedly foggy and disjointed.

Trump, 78, made wild assertions and lied repeatedly, remaining unapologetic about his alternate-reality claims about the 2020 election, while avoiding a grievance-filled rant. Biden, 81, spoke rapidly and appeared to meander through his answers, fumbling at the end of sentences even as he accused Trump of being a liar and a threat to democracy.

Here’s what else to know:

— Opening salvos: The debate started with a dramatic contrast between the two candidates. Trump responded to questions about taxes, inflation and abortion with aggression and discipline, repeatedly criticizing Biden’s administration. Biden was halting and over-programmed, losing his train of thought on the subjects of Medicare and abortion. Biden spoke rapidly, sometimes appearing to mumble his words.

— Trump pounces early: Trump seized on Biden’s shakiness and early stumbles to underscore Republican questions about the president’s mental capacity. When Biden trailed off during an answer on immigration, Trump quickly offered: “I really don’t know what he said at the end of that sentence. I don’t think he knows what he said, either.” After an answer by Biden on immigration, Trump claimed that the president had allowed terrorists and criminals to cross the border. “I call it Biden migrant crime,” Trump said.

— Democrats worry about Biden’s performance: Within minutes of the debate’s start, Democrats began wringing their hands about Biden’s performance. On social media, in chats and in emails, the president’s supporters freaked out about the president’s trembling voice, his disjointed answers and his apparent confusion during some of his responses. Concerns about Biden’s age, which have been simmering for months, burst into public view before the debate was over.

— Biden and Trump get personal: The president lashed out at his rival in ways that might have once been unheard-of on a presidential debate stage, noting that Trump was the “only person on this stage that is a convicted felon” and bringing up lawsuits accusing him of molesting a woman and having sex with a porn star “on the night while your wife was pregnant.” He said Trump had the “morals of an alley cat.” Trump responded by referring to the criminal conviction of Biden’s son Hunter, saying, “His son is a convicted felon at a very high level.”

— Trump ignores moderators: Trump largely ignored questions from the moderators, using his time to boast about himself and attack Biden. The former president did not repeatedly interrupt his rival as he did at the first debate in 2020. But he spent his time repeatedly hammering Biden as “the worst president” in the history of the country. Several times, Trump finished his answers without taking his full time, prompting the moderators to repeat the original question.

— Trump’s blizzard of lies: Trump reprised his habit of offering a flurry of assertions that are false, something that he honed during his first two campaigns and as president. Fact-checkers caught him being misleading on the damage to Social Security, the environment, the Jan. 6, 2021, riot and the increased cost of food. He repeated his false claims that the Justice Department had been involved in the state cases against him.

— Biden sharpens in defense of NATO: In one of Biden’s strongest moments, he forcefully accused Trump of being willing to abandon Ukraine in the face of Russian aggression. “I’ve never heard so much foolishness,” the president said. “This, the guy who wants to get out of NATO. Are you going to stay in NATO?” The comment punctuated a fierce back and forth over the role of the United States in the world. Trump’s retort: “The only reason that he can play games with NATO is because I got them to put up hundreds of billions of dollars.”

— Biden stumbles on abortion: Coming into the debate, abortion was supposed to be one of the strongest issues for Biden. But his answer to a question about the procedure prompted concern among his allies. He started by talking about Trump’s desire to let states decide whether abortion is legal. But he stumbled through a story about a young woman “who just was murdered” and referred to a funeral that Trump attended. The intent appeared to be to call into question the former president’s claims about immigrants living in the U.S. illegally raping women, but Biden’s stumbles made it difficult to understand. “There’s a lot of young women to be raped by their, by their in-laws, by their, by their spouses, brothers and sisters. It’s just ridiculous.”