The average poll similarly shows Trump's approval rating hovering around 40%, while his disapproval rating is above 55%.
What's the point: Trump's approval rating isn't getting any better. In the polls, he is continuing to lose to former Vice President Joe Biden by double-digits. Trump could win a second term, but there is no clear path to doing so.
If Trump does go on to lose in November, he doesn't just need to worry about losing to Biden. Trump needs to worry about the fact that the history books are probably going to put him down as a below average president, if not one of the worst.
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.
View Trump and Biden head-to-head polling
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.
View 2020 presidential election polling
I'd bet Trump would dip even lower given where the historians already have him. The average of the APSA and Siena polls put Trump at 43rd, which ties him for last with Buchanan.
At the time the APSA poll was published, I urged caution since it was one poll done early in Trump's presidency. Now, we have the Siena poll as well. Additionally, more voters by far said Trump was the worst president since World War II in a 2018 Quinnipiac University poll. (Few ranked him as the best, which is very different from a similar poll taken during Obama's second term.)
Importantly, these early rankings are generally predictive of later rankings in a look back at presidents since Franklin Roosevelt (the first modern presidential ranking was completed three years after he last held office).
Since 1948, the final historian rankings of a presiden