A Trump-Clinton Analogy That Could Give Biden Comfort

There’s no precedent for a presidential candidate to face doubts as serious over age and mental acuity as President Biden faces today.

But there is precedent for a candidate to face similarly serious, fundamental doubts about handling the job of president. It’s a precedent that lends itself to a somewhat peculiar but still useful comparison to today.

That precedent is Donald J. Trump in 2016.

The 2016-era concerns about Mr. Trump’s fitness for office, as reflected in polling, suggested that a majority of voters harbored the most basic doubts about his ability to do the job. In Mr. Biden’s case, those doubts have stemmed from his age. For Mr. Trump, it was his lack of experience and unpresidential temperament.

The doubts about Mr. Trump set the stage for a volatile campaign, as a crucial segment of traditional Republican-leaning voters recoiled at their party’s nominee in pre-election polls. At times, Mr. Trump’s percentage of support among Republican-leaning voters was as low as the 70s, and it was in the 80s as the election approached. Today, Mr. Biden finds himself in a somewhat similar position, as defections among Black, Hispanic and younger voters have given Mr. Trump a narrow lead in the early polls.

Mr. Trump’s weakness among Republican-leaning voters wasn’t exclusively because they questioned whether he could do the job effectively. Many Republicans were repelled by his insults against ethnic groups or