I think this article made an important distinction that I have not seen before. Republican presidential candidates scare potential voters from the left with their rhetoric, but also scare voters on the right with their likely inaction.
Democrats campaign on their promise of creating new government programs to solve programs. When elected, they can't wait to create these new programs. Republicans campaign on balancing the budget and limiting government. But when elected, they do the opposite, creating new government programs just like the democrats.
Thus republican candidates scare leftist voters with their rhetoric and disappoint right-leaning voters with their actions. The worst of both worlds.