Whatever sliver of moderate Republicans the Dems can get they should take.
This election isn't a contest between Republicans and Democrats. It's between autocrats and people who want democracy to continue. That's more important than any other consideration.
If you divide the US between Dems and Republicans, and you lose, you'll regret not gathering up as many Rule-of-law Republicans as you can. And if anyone will hoover them up, Cheney will.
No Democrat will vote for Trump, whoever is on the ticket.