Absolutely no reason to jettison millions of fellow Americans.
All Democrats need to do is to run on a more centralist program, and get it spearheaded by a youngish candidate with no skeletons in their background. Preferably some one with a military background...some one who can look Trump in the eye, and say “I served, when you didn’t”.
Trump would then lose heavily.
But...I suspect...that such a simple strategy will elude the Democrats, and Trump may win again in 2020.