The establishment GOP is pulling every trick they have to block Trump from getting the required 1237 delegates to win the nomination before the summer convention and if they succeed, anything can happen.
If Trump does hold on and become the de facto 2016 presidential nominee, conservatives will eventually rally around a Trump nomination to win the Oval office, but will always have their get-out-of-jail card right in their back pockets. They've already expressed in no certain terms that Donald Trump is not a conservative, so when he is resoundingly beaten in the general election they can wash their hands of him and say once again, conservatism doesn't fail, only the candidate does.
However, if Cruz gets the nomination then that card in their back pocket is null and void. When he loses they will have nothing to complain about except maybe to blame the mainstream media for the loss.He's right about that. I have also been writing about the awful choice these Republicans have to make deciding whether they'd rather get thumped with Trump or lose with Cruz. It's assumed that people like Jeb Bush or Lindsay Graham are just so antagonistic toward Trump that they're hold their noses for Cruz (or unrealistically hope for some gambit at the the convention that will spare them either.) But there's likely another motive: maybe they'll be able to finally purge some of the Tea Party poison if they do manage to nominate a true blue, 100% pure conservative like Cruz and he loses big. The movement will obviously find some good rational as to why he too failed to be conservative enough. But it's not going to hold water.