By Lowering the Debate Bar for Biden, Has Trump Set a Trap for Himself?

But he said Mr. Biden had bigger issues to overcome than simply exceeding that low bar. “What I’m seeing in these battleground Senate polls is that people know that Joe Biden was Obama’s vice president, and that he’s been around for a long time. They don’t really know the guy,” he said. “The Biden voter is simply an anti-Trump voter. What if he fails to make this about what he’s for and what he’s about?”

The Biden campaign, meanwhile, has been telling people that no debate outcome will fundamentally change the contours of a race that has been defined, since March, by the president’s handling of the pandemic, even if the president performs well onstage. Mr. Biden’s hope on Tuesday night, according to someone familiar with the campaign’s strategy, is to continue making the election about the president’s accountability for the lives lost to the coronavirus, while trying to show what it would look like to have a leader in charge who doesn’t need to be fact-checked in real time, and who attempts to bring the country together.

Democrats are concerned that Mr. Trump may be successful at making Mr. Biden lose his temper by talking about Hunter Biden. The president has repeatedly talked about the younger Mr. Biden in the past week, and Republicans have tried to push negative coverage about him in the news media.

In the past, Mr. Biden has struggled to come up with a definitive response to questions about his son’s work overseas and whether it raised questions about conflicts of interest while his father was in office. While Mr. Biden’s empathy and his love for his children have been calling cards for voters who like him, they have made it challenging for him to put those questions to rest.

Mr. Rove accused him of trying to “defend the indefensible.”

But it’s not clear that simply unsettling Mr. Biden with murky accusations of corruption will necessarily have the intended effect on the audience watching at home. “Trump has to try and change public perceptions of him,” said David Axelrod, a former top adviser to President Barack Obama. “That is not going to do it.”

Mr. Trump’s allies are also concerned that the president, who is generally cocooned from people who oppose him, will be unable to resist the temptation to defend himself from Mr. Biden’s face-to-face criticisms.

Mr. O’Donnell anticipated that Mr. Trump would “try to put pressure” on Mr. Biden, through tactics like interruption, name-calling and a physically dominating presence onstage.