Take a look at the 13 incumbent elections dating all the way back to 1940. Usually going all the way back in time will lead you to find a lot of volatile campaigns, as more modern ones tend to be more steady.

Yet, since 1940, the final result differs from the polls at this point by an average of just 7 points. The median difference is only about 4.5 points.
View Trump and Biden head-to-head polling

These should be quite worrisome for Trump given he’s already down double-digits, and there’s no guarantee any polling miss would benefit him.

Indeed, we can translate past polling to give us odds about the current election. At least 8-in-10 to 9-in-10 times based solely on the horserace polling, Biden would be expected to take more votes in the fall.

More troublesome for Trump: no one in an incumbent presidential election has been polling above 50% at this point like Biden and gone on to lose.