You don't have to become a Democrat
My suburban Republican friends need to give up on the idea that while they don't like Trump, they just can't bring themselves to vote for a Democrat, so maybe the congressional Republicans will keep him in check for the next six and a half years. You cannot acknowledge that Trump is incompetent at best and presents a true danger to our democracy, and then turn around and vote for the people that are rubber-stamping his tirades and enabling him.
You don't have to become a Democrat to vote for one -- once the keys are taken away from the current president, then you can go back to voting for actual conservatives of whatever stripe. But for 2018 and 2020, swallow your distaste for all things left of center and help save our country from itself. Your children, your parents, your neighbors, and the whole world will thank you.