All in all, Biden is currently +10 against Trump in the general election. Beto is +6. And this is all happening while Trump is having one of the best stretches of his term. He’s currently hovering near his best-ever approval rating where he’s “only” -10.
What are those numbers going to look like when he’s having one of his bad weeks?
Or think about it this way: Trump’s reelect hinges upon him holding all of his 2016 states and praying for an inside straight again. His chances of flipping anything other than New Hampshire are awfully small.
On the other hand, if either Biden or Beto is the nominee, Michigan, Arizona, North Carolina, Pennsylvania, Wisconsin, and Texas—Texas!—are all live propositions for the Democrats.