I assume those people didn’t vote for Trump in 2016, so if they vote for Kasich in 2020, would it make any difference? In this situation, aren’t those people really potential democrat voters?
Some of them might have voted for Trump in 2016, due to Hillary being the alternative. There were a lot of people who were never trumpers to very near the end, then came along. If they can vote for Kasich and keep their consciences clear, they might. Enough of them to make a difference. You are trying to use logic to explain why idiots like Kasich, Flake, Kristol, etc. think.