The only way I can see Trump can become president is to do something blatantly anti-democratic or fascist, such as literally rig the election, or mobilize the military or various militias against the people, or forced open voting where everyone has to publicly declare who they are voting for in front of officials and police—something along those lines. Third-world republic-type tactics.
But now that everyone knows what Trump and the Republicans are all about, they’ve pretty much established the extent of their voter base. Much of what they believe, and how they act, in is inimical to what most Americans believe and want (although a substantial minority of people think they are just fucking dandy). But I simply can’t see where in an open first-world democracy, people who’ve been voting Democratic, or even flipping between the two based on the economic concerns of a specific moment in time, would conclude, “You know, I didn’t know much about these Republicans before, but I really like the way they go after the Biden Crime Family and how they want to slam the door shut in all foreigners’ faces. I really like the cut of their jib.” I can see more and more people peeling off from the red hat margins as the Republicans, both elected and candidates, become increasingly repugnant, but I can’t see how normal gentle people who have nothing against entire other groups of people simply peel off Biden et al and move over to this version of the Republicans.
I suppose the Republicans could try to orchestrate something terrible economically or safety-wise that would result in tens of millions of people’s retirements or fortunes wiped out, or millions dead, that they can blame the Democrats for, but as long as there is a free and fair election in which they are relying on the people to “do the right thing”, even that would be a risky proposition. It’s always risky to rely on the free will of the voters. That’s why autocrats and fascists don’t.