There are lots of folks who like Republicans but hate the Republican establishment. I imagine Rubio could really fire up his supporters by portraying Crist as the vanquished puppet of the evil party establishment, at least as much as he could by portraying Crist as a liberal.
Yeah, but that only works in primaries. The argument you describe is too complicated for a political point, it's not easily digestible, as Rubio is now the candidate of the evil party establishment. There's no foundation for Rubio to make the anti-GOP establishment argument in the general election.
I just don't how "vanquished puppet" is a winning argument, except in political circles like this forum, it's actually a contradiction. If he's an establishment puppet, why is he vetoing GOP bills and running as an Independent? If he's vanquished, why is he leading in the polls?
Good political arguments are simple. They don't involve rhetorical pivots, hypotheticals, etcetc. A political argument, just like branding in the private sector, conveys an essential message. Obama, to the frustration of his opponents in '08, took this to heart and really let two, yes, two, words define his entire existence for swing voters and to motivate the faithful. The fact that I don't even have to say what those two words are is evidence enough of their effectiveness.
Rubio's winning arguments are taxes and jobs, he's not going to win if he makes complicated criticisms of one of his two opponents key to his campaign. I haven't studied the subject, but it'd be my guess that negative campaigns are far less effective in a three-way brawl, as negative campaigns always reduce the likability of the attacker in the hope that the attacked candidate will be hurt more.