Donald Trump has many Republicans running scared. After Marco Rubio's withdrawal, the establishment republicans are looking for anyone to save them. Enter Ted Cruz. Cruz has made a great many enemies among establishment Republicans. He does not play ball well. As a Senator, he has called his own Republican leader a liar, shut down the government when it hurt Republicans but gave him more personal "cred" among hardcore conservatives, and has pushed agendas designed to benefit himself over the party. As a result, many have shunned the Cruz campaign. Lindsey Graham commented “If you killed Ted Cruz on the floor of the Senate, and the trial was in the Senate, nobody would convict you.”
Now that Trump looks like he is on a serious glide path to the nomination, establishment Republicans are beginning to hold their noses and embrace Cruz. Sen. Graham, who also once said supporting Cruz was the equivalent of taking poison has decided to grab the cup of hemlock in both hands and drink heavily by endorsing Cruz. Former nominee Mitt Romney has also said he would support Cruz in the upcoming Utah Caucus. Apparently he is the lesser of two evils.
What about John Kasich? He is still running and has the benefit of not being either Trump or Cruz. Kasich's numbers are just too low. Having won only his home State and nothing else, his delegate count is too far behind. He can only be a spoiler at this point. Going into many large winner take all states, he is seen as dividing the anti-Trump vote and giving him the win. It must become a two person race and Kasich is clearly number three.
The next races in Arizona and Utah are almost certain losers for Kasich. This will only increase momentum of calls for him to go away. He may be holding out for many of the big east coast and west coast primaries still to come, but his poll numbers don't show him winning. Party elders have decided that Kasich must go.
At first blush, moving to Cruz may be an odd choice. Both Cruz and Trump are divisive candidates with high negatives. But Trump has brought in many more independents to the polls. He also makes several swing states competitive or at least in question. By comparison, Cruz has a more predictable appeal to hard core party conservatives and few others. His ability to bring in independents or win swing states seems near impossible. Cruz seems like a certain loss in the general election, while Trump could actually win.
Republicans are looking beyond the White House in 2016 though. They worry that Trump will mobilize more voters to support the Democratic candidate and that those increased numbers will cause many Republican Senators and Representatives to lose their seats. Remember, 2016 is six years after the 2010 Republican congressional landslide. Republican incumbent Senate seats are up for election in 24 of 34 states. Republican Senators have a lot to lose.
For many establishment Republicans, an even scarier scenario to a massive electoral loss is if Trump win the Presidency. They fear President Trump would be an absolute disaster. Part of the fear is that Trump has discussed his policy goals in such vague terms that no one is really sure what he will do. They do know that he will energize the left in way that no President has done since Ronald Reagan, while at the same time fail to inspire the right as Reagan also did. Trump will tarnish the Republican brand, contributing to even more losses in future years. Trump will redefine the party in a way that will push a generation of Hispanics and other minorities, as well as many women, toward the Democrats.
Trump is more likely to start another damaging war. The disastrous Iraq war tarnished the Republicans, but can be written of as an anomaly. A second such war becomes part of a pattern that will send voters running out the door. Trump may also start a devastating trade war which could cripple the economy. The possibilities of such disasters in such a wild card and untested candidate are just too numerous to mention.
If Cruz wins the nomination but loses the general election, Republicans get to fight another day and have a much better opportunity to retake the White House in four years. No one, even among most Republicans, believes that Cruz has a serious chance of winning the general. Long term though, establishment Republicans fear a Trump win more than they do a Cruz loss.