Then they don’t need to worry about your vote and are stuck competing for the remaining voters
Well, they would get my vote if they changed their policies and behaviour. If you vote them no matter what they dont have to fight for it. (Note i am not a US citizen but the same principles apply. I have similar dissapointment with the formerly progressive parties in my country moving to the right)
And we can also observe this empirically with the current election. The Dems were so tone deaf that they thought to compete over Reps not too happy with Trump, fielding people like Dick fucking Cheney as their advocates. Meanwhile they lost a lot of votes they expected to just have secure because they expected the voters to be blindly loyal hence irrelevant to their strategy.