I think you have hit the nail on the head here. If Trump wins, Cruz and Kasich's presidential chances are over forever and their chances for other high office are diminished. If Trump loses, Cruz and Kasich will be blamed and the result will be the same.
The smart thing would have been to urge others to vote strait R or say nothing at all. In my opinion, Cruz and Kasich have both ended their presidential chances forever.
Pence, Walker, Rubio, Perry and probably others as well, will look classy by comparison to sore-losers Cruz, Kasich and don't forget JebBush.
Cruz pitched to the faction that I call "Narrow But Loud," not a path to victory on a national scale.
His unappealing persona does not portend to making that faction bigger. Very poor political judgment, over and over.