First and foremost because Biden isn’t Clinton.
Let me be clear. Trump can beat Biden. It’s entirely possible. It’s just looking less and less likely as election day approaches.
This is Five Thirty Eight’s 2020 Election Forecast Snake Chart which I find to be a very easy way to look at what the election forecasts look like as far as what it takes to win and how competitive each state is.
The closer you get to the middle of the snake, the more competitive a state is. If it’s tinted red, it’s leaning Trump, if it’s tinted blue, it’s leaning Biden.
The line in the middle shows where the 270 electoral vote threshold is crossed. The length of the state in the snake is indicative of the number of electoral votes it represents.
In 2016, Trump won everything on this snake up to Minnesota with the exception of Nevada
There are 8 states right now that are leaning blue that all went for Trump in 2016. Biden needs three of them, two if one of those is Florida.
That said, the projections looked similar leading in to the final weeks of 2016. What happened was a few states, most notably Michigan, Pennsylvania and Wisconsin which were all projected to go to Clinton by a couple of percentage points all went instead to Trump by the thinnest of margins. Trump won the election by winning those three states by a combined margin of 77,744 votes.
The problem for Trump this time is twofold.
First, while he hasn’t lost much of his core following, he hasn’t added to it either. Meanwhile the fringes, the ones who held their noses and voted for him last time are melting away.
Defectors are a major problem in an election because a defector counts as 2, you lost a vote you had last time, and the other side picked it up. To understand how big of a problem that is, in Michigan, if nothing else changed and 5,353 of the 2,279,543 people who voted for Trump in that state defect, Michigan’s 16 Electoral votes slide away from Trump’s total and hop on top of Biden’s, a 32 vote swing. That’s 0.23% of the people who voted for Trump in Michigan in 2016.
New voters are also a problem for Trump. 52% of People who didn’t vote in 2016 say they’re voting for Biden, only 32% say they will vote for Trump. Biden also leads by 11 points among voters who voted third party in 2016 and do not intend to do so this year.
Second, as I said, Biden isn’t Hillary. And the point of that is that no matter what you think of Trump, Hillary or Biden, it is clear that Hillary inspired a LOT of irrational hate. I don’t just mean disapproval, I mean hate, on the same level that Trump does. Biden doesn’t inspire that kind of hate. Disapproval, sure. Dislike, sure. But not that same seething hatred people felt for Hillary.
Especially look at the difference among independents, more than half of whom strongly disliked Clinton: