Butegiggedge is probably the smartest person up there and I like his ability to lay smack in DJT. He's the only vet we've seen in a few decades. Of course, there's that one thing about him though. America probably isn't ready for that yet.
Sanders has the army of supporters much like DJT has. He would also destroy Trump in a debate, but I don't expect DJT to participate in any of those anyways. Of course, he's a bit goofy and old. Tough for me to imagine a President Sanders.
Biden is in over his head at this point. He could have probably beat Trump in 16, but he's lost it.
Those other brawds, no chance.
Tulsi could have a decent career in pron.

I pick Tulsi.