President Trump can’t seem to help himself. Though he may regret it after Tuesday night’s presidential debate, he continues to lower expectations around how well Joe Biden will perform in the head-to-head confrontation.

Trump and his allies have for weeks been disparaging Biden’s mental and physical capacities. The president has described Biden’s debate appearances during the Democratic primary season as “a disaster” and “grossly incompetent.” His campaign has circulated manipulated videos that make the former vice president appear doddering and incoherent.

More recently, Trump has even made a ridiculous and unwarranted demand that Biden submit to a drug test before they face off on Tuesday.

“His Debate performances have been record setting UNEVEN, to put it mildly. Only drugs could have caused this discrepancy???” he tweeted.

Trump is right that Biden became noticeably more sure-footed and confident during the 11 debates in which he participated while running for the Democratic nomination. That’s what practice, effort and experience will do for a candidate.

The real Biden does not resemble the caricature that Trump and his campaign have confected. And he has wisely suspended his campaign so that he will be in fighting form when he takes the stage in Cleveland on Tuesday night.

Meanwhile, if recent history is any indicator, Trump is the one who should be sweating.

Incumbent presidents have, more often than not, stumbled in their first debates, in part because they approach them both overconfident and underprepared. It happened to Gerald Ford in 1976, Jimmy Carter in 1980, Ronald Reagan in 1984, George W. Bush in 2004 and Barack Obama in 2012.

For George H.W. Bush, disaster struck in the second debate of 1992, when television cameras caught him checking his watch as an audience member asked him how deeply the recession had personally affected him. Years later, the elder Bush acknowledged what he had been thinking at that moment: “Only 10 more minutes of this crap.”

The current president appears to be following this historical trend. Trump has said he doesn’t need to buckle down on briefing books or load down his schedule with practice sessions and mock debates. “I sort of prepare every day by just doing what I’m doing,” he has claimed.

But unlike four years ago, he is no longer running as an insurgent outsider. Trump is now an unpopular president who will be called upon to defend his record, which includes mismanaging the federal government’s response to the covid-19 pandemic and fueling racial tensions. Meanwhile, thousands of records newly unearthed by the New York Times reveal him to have been both a lousy businessman and an apparent tax chiseler.

Biden, by contrast, goes into the debate with a durable lead in the polls that has put him on track to win this race, possibly by a wide margin. If he does well enough, he could close the sale with the American electorate.

So what does he need to do?

As Philippe Reines, who played Trump during 2016 Democratic nominee Hillary Clinton’s practice sessions, has pointed out, Trump is both a bad debater and difficult to debate.

Brett O’Donnell, a Republican strategist who specializes in coaching candidates for debates, puts it this way: “He doesn’t get held to the same rules that conventional candidates do.”

But by now, the country has seen his act. Voters know it’s a safe bet that Trump will lie, make outrageous claims and lob unfounded accusations at Biden.

The Democratic nominee’s biggest challenge may be to control his temper and refrain from following the president down every rabbit hole. A dismissive, “C’mon, man,” here and there may be all it takes.

The expectations game can work both ways. Trump has indeed laid a trap. What he doesn’t seem to understand is that he is the one who appears most likely to step into it.

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