When Trump closed the gap in the increasingly old days of the 2016 campaign, he had to convince very few Clinton supporters to vote for him. Trump just had to pick up the support of those who are not determined or support a third-party candidate.
Right now, Trump’s path will be difficult if not impossible to win if he doesn’t take voters who are already with Biden.
Nor are other historical examples too kind to Trump. The only other challenger at this point who had or hovered about 50% was Jimmy Carter in 1976. He won.
Here’s Trump’s problem: The average poll at the moment was held by Truman’s Republican opponent Thomas Dewey with 46%. So even if Biden’s advantage over Trump in these polls is 2 points greater than Dewey’s was over Truman (south of 9 points), Biden earned about 5 points more voter support. Dewey simply did not have voters committing to him in the same way as at this time.
Indeed, Trump’s need to convince those who are not already in another camp is reflected in another way. His disapproval rating in the average survey is 54%. No other president at this point in the electoral period had such disapproval before he was given the opportunity to win a second term. Truman’s was 47%, as his deviation score took away 39%. However, it was the majority of Americans who at least disapproved of him.
In 2016, Trump proved he can defy history. If he wins a second term in 2020, Trump will have to do it.