Hinder in the primary by pissing off all the Trumpistas.
Serious question: How many Trumpistas will there still be three years from now? For me, it remains an open question as to how both the GOP primary electorate and movement conservative elites write the revisionist history of Clinton's victory this year, should she win. I'm not sure how much attention will be paid to who supported Trump and who didn't. It's possible that Trump will simply be retroactively written off as an interloper to the party who blundered away a winnable election, and people won't want to talk about him anymore by the time the 2020 primaries are upon us.