Anything indeed can happen, but I don't think that Harris entering the race - a prospect that was actually very much in the cards from the very creation of Biden/Harris ticket in 2020 - will change that much, at least not by itself. At this point, it looks like the race will be only slightly closer and more exciting than it looked a week ago, and only because the Democratic base is slightly less demoralised than it used to be and not because of undecided swing voter suddenly being convinced that Harris is the best thing since the invention of sliced bread.

A lot will depend on whether the charade with Biden as "President" will continue or Harris actually doing what she was supposed to do and actually take presidential duties. If she doesn't, she would be even less likely to do it via election.