did Trump get elected because of a desire for him and his policies or was it because of a rejection of Harris and her policies?
Not even close. Rejection. More to the point, rejection of Democrats being in charge.
How do we know that? Go back to 2016 and ask how Hillary, despite having better favorable ratings then Trump, still lost. In both elections,when a persuade able voter (swing voter) has two bad options (in his mind) then how are those voters going to vote? They are going to break for the least bad option.
Ask yourself this. The odds should be 50% when both sides have the same favorable ratings. But that isn't going to happen when one Party is the "Party of no". Therefore, the voter concludes that he can do the least damage by voting for the "Party or candidate of no". (way over simplified) So Republicans have an automatic advantage in elections of two bad choices.
Keep in mind, that the typical swing voter is not heavily engaged to the point of understanding the nuances of just how dangerous an option someone like Trump is. Therefore, the brand perception of the Party is of vital importance.
Its far easier for a Senate candidate to put some distance between himself and his Party. For national candidate, much harder. It was interesting that in focus groups, there were some swing voters that couldn't give Harris much credit for moderating her views on some things. They just couldn't believe knowing her history and knowing her Party.
So if Democrats maintain their negative perception then they will underperform the 50%winning threshold. EXCEPT as in 2020 when recent history shows the swing voter who the worst option REALLY is.
Frankly, Democrats should do some cleanup so they can outperform the 50% threshold.