Republicans are motivated almost exclusively by fear, so there's no shortage of things Trump our any other demagogue would be able to exploit and rally the feeble-minded around.  The thing that drives republicans now is their fear that they're being replaced in the economy and losing economic and political power, which is why they fight so hard to undermine democracy now.  When they say "make America great again" they're necessarily invoking a time when white people had more political power.  They're so threatened by actual democracy they'll storm the the capital in an attempt to stop it.