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While I have my problems with historical rankings of presidents as an exercise (e.g. the graders tend to be far more liberal than the population at large), they are a good guide into understanding how history remembers presidents. The presidents viewed at the top of the lists (George Washington and Abraham Lincoln historically) or near the top (Ronald Reagan) tend to be thought of fondly. Meanwhile, those at or near the bottom of the list (such as James Buchanan and Andrew Johnson) are generally thought of as failures as president.

The biggest factor separating those who rate highly and those who don't is whether they win a second term in office. Take a look at an average ranking by experts in the 2018 American Political Science Association poll and 2018 Siena College poll.

The average ranking for presidents who win a second term is 14th. That's well above average given we've had 44 presidents. None ranked lower than 32nd (George W. Bush). The best was the top spot overall (Washington).

The average for presidents who did not win a second term is 30th. That's well below average. None of the presidents who didn't have a second term ranked higher than 13th (John Kennedy, who was assassinated). The worst was last overall (Buchanan).

Just on this basis alone, you'd think that Trump would probably go down as below average if he lost in November. We wouldn't know quite where he'd land, but it'd be a pretty good bet that he wouldn't finish in the top half.

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