Kasich in a unified party could probably beat Clinton or Sanders, considering Clinton's negatives, and Bernie's S-word stigma, but if they nominate Kasich, the party is most certainly split into two, or maybe three factions. For the already disgruntled with Republicans ultra-conservative crowd will have had it, and start their own Party of Constitutionalism and Religious Liberty, or whatever, and Trump's Make America white again party. Anti-clinton sanders sentiment wont be enough to put humpty back together.

and I think Ryan/Romney would be even worse for them and give even more of a sense that the game is rigged.