The Republicans are coming together
The Democrats are falling apart
Let's be clear, there are no Republicans any more.
It's Trumpism and MAGA. Any "Republican" is now an independent or a registered Democrat.
Trump will not get more votes than he did in 2020. He just won't. There is nothing to suggest he will. He has done nothing to expand his base. His true believers and those who simply want power are the same as they were 4 years ago.
Now with your second point, yes that is a concern. But even Democrats falling apart are going to vote for whoever the Democrat is that is ultimately against Trump. The bigger concern is people just throwing their hands up in the air and staying home in 2024. That's bad for Democrats. Which is why we need to get this nominee situation resolved as soon as possible.