Being left leaning myself, I can't see me voting again for a Clinton, and I can't see voting for Warren either. Might as well say I'm a voter without a candidate, if I were to tow the party line. The democrat politicians I really like, will not run. There's one independent I would have voted for, but he is way too far left leaning progressive.
When you say old guard GOP, I think of Reganites, not of a Bush era GOP member. The old ones knew how to wheel and deal and how to give what others wanted, while walking away with something republican constituents wanted.
The herd of politicians we have these days would make the established GOP and democrats who have passed on turn over in their graves.