You may not think so, because you are an American conservative...and American conservatives think that anyone to the left of Genghis Khan is a very far left leftist, commie, pinko, socialist pig.
I am not a Democrat, but I know many Democrats...and I know there are far left (not as far left as I on social issues)...slightly left AND MODERATE CONSERVATIVES in that party.
There is no where for the "slightly left" and moderates to go...and they were not driven out. Today's American conservatives simply are willfully blind to their existence. Most would not even think about gravitating to the Republican Party.
You are wrong, but I don't expect to convince you of that. Live with your mistaken opinion that ALL (or even most) Democrats are radicals.