he'd have to have the active, energetic support of a significant portion of the republican establishment (by which i mean, like, actual governors and senators, not jokes like bill kristol or whoëver) - and even then, 20% is an incredibly optimistic target
This -- Trump has already shot himself in the foot so much that if the Johnson/Weld team is competent they'll be able to achieve this by fall (they're clearly already working on getting Mitt Romney on board, for instance). Even then, to eclipse 20% Hillary would have to actually get indicted, or somehow disqualified and fallen to Trump levels, so that a similar group of Democratic politicians starts to emerge as well.
