Who cares that you don't believe Trump to do something you know your candidate won't do at all? It's a stupid and infantile reason to doom the country. "I don't believe your candidate really will save the country from permanent Democratic control! So I'm going to choose the candidate who guarantees it!"
No, it’s more that Trump is so much worse on pretty much every issue, and I’m not willing to throw everything else away just for the *slight* chance that he’ll actually be better on immigration.