There’s a very good reason for Rubio and Cruz not to destroy Trump

You can make a case that Cruz should prefer the GOP nominate Trump instead of Rubio, or that Rubio should prefer Trump over Cruz. Cruz and Rubio are both young and both want to be president. Assuming they don’t run on the same ticket, the chances would appear low that both men will reach the White House someday. If Cruz wins the nomination and the general election, Rubio has to wait eight more years for another shot, and he probably starts that election an underdog to Cruz’s vice president. The same is true in reverse.

A Trump win very possibly shortens that wait. General election polls are notoriously unreliable at this stage in the election, but they suggest he is more likely to lose in November than Rubio or Cruz would be, creating another open primary in 2020. Even if Trump beats the Democratic nominee, he could prove ripe for a primary challenge in four years if he, say, pushed a single-payer health care plan through Congress.

In those scenarios, either Cruz or Rubio would prefer to be the second-place finished in a three-man race that ends with Trump being nominated. It would position the runner-up well for the next contested primary, whenever that might be. It would blunt the incentives for either man to drop out.