A good friend of mine, a Republican former Hill staffer and Bush Administration (W) official, tells me that as of this week he cast his support to Kasich. As he sees it, Trump and Cruz would spell disaster for the party. He believes that while Trump and Cruz together get around 50% of the Republican vote, they can't make much headway into the other half. He would even vote for Bernie rather than them and believes many other Republicans would too. He discounts Bush – whom he believes would have been a better president than his brother – because of dynasty fatigue and distrust from the Bush presidents not keeping their word (on taxes and war). Rubio might be able to recover but Kasich has more experience.
My friend also also believes Bernie may prevail over Hillary because of her negatives. He thinks Sanders would win over either Trump or Cruz but not with enough votes to bring in a Democratic majority in either house. (He would find a divided government, and continued political stalemate, an acceptable outcome.)
This is the Republican conundrum. A significant part of the Republican electorate is deeply distressed about the prospect of either Trump or Cruz winning the nomination. But they don't yet see a clear path for anyone who may be able to stop them. The possibility that the peculiar political circumstances of this year – an electorate wanting something new and aligned along the “extreme” wings of the two parties – could lead to a Trump vs Sanders match-up is startling. But the Fat Lady hasn't sung yet and things may sort out a bit come South Carolina. However, if Trump wins there and the non-Trump/Cruz candidates bunch up without any clear breakout, the Republican Party will be in difficult straits.