A Full Guide to the Final Presidential Debate

From the earliest days of this campaign, Mr. Trump has sought to damage Mr. Biden by disparaging the business dealings of his son Hunter and claiming that Mr. Biden, as vice president, embraced policies that allowed the younger Mr. Biden to enrich himself in his dealings with Ukraine and China. These allegations, many of them unproven or questionable, have circulated widely on Fox News and right-wing social media. But, to the frustration of the president and his advisers, they have so far not appeared to break through beyond that audience.

The Trump campaign could not have been clearer in recent days in telegraphing that Mr. Trump intends to use this final stage to raise the allegations again. “If the media won’t ask Joe Biden these questions, the president will, and there will be no escape for Biden,” Bill Stepien, the president’s campaign manager, said in a statement.

At the last debate, when pressed by Mr. Trump on the issue, Mr. Biden appeared to struggle a bit with the question; presumably he will be better prepared on Thursday. For Mr. Trump, the goal is to tarnish his opponent. For Mr. Biden, at the very least, the attacks on his son might goad him into making the kinds of mistakes that might dominate a news cycle or two.

Mr. Biden managed to elude answering questions from Mr. Trump at the first debate about whether he would, as president, support expanding the number of seats on the Supreme Court. He is under pressure from many Democrats who see an expanded court as the best way to counter Mr. Trump’s success in installing two (and very likely soon to be three) members of the court.

After weeks of declining to clarify his position, Mr. Biden said in an interview made public on Thursday that if elected, he would establish a bipartisan commission of scholars to study a possible court overhaul more broadly.

“I will ask them to, over 180 days, come back to me with recommendations as to how to reform the court system because it’s getting out of whack,” he told CBS News’s Norah O’Donnell, according to an interview excerpt that is expected to be broadcast in full Sunday on “60 Minutes.”

Previously, Mr. Biden had said that a firm answer on expanding the court would take attention away from what he said was the main issue: the decision by Republicans and Mr. Trump to rush through the nomination of Judge Barrett to fill the vacancy created by the death of Justice Ruth Bader Ginsburg.