The only reason I can see that this is happening is because some on the left (or left-middle) are a bit nervous about what they have bought (or tricked) into.
We all have to remember that there are millions of low-info Democrats, and millions of Republicans for that matter, who vote the way they do because their parents and grandparents voted that way. Those low-info Democrats are now getting perhaps their first real look at the zombie they voted for President, and the cackling witch they voted for Vice President.