although i understand dig's model, i think he overrates rubio's appeal. like you, clo, i see kasich as more of a uniter of the old conservatives.
i suspect bush voters mostly turn to kasich. so you have four people in the race once carson surrenders. i think carson's folks may also break for kasich (because not cruz, not trump, not rubio).
trump in low-mid 30s. cruz, rubio, kasich in low-mid 20s. everyone waiting for someone else to give up all the way to the convention, unless kasich gives up after march 15.
trump wins or brokered convention splits the party and trump launches an independent bid against the chosen republican.
total chaos. the winner is the democratic pick, which starts to look like hrc after sanders' momentum finally tailed off in nevada.