From Tim Mak writing at the Daily Beast:

Donald Trump and Ted Cruz’s mutual admiration is turning into a conservative bromance—one that could have a huge strategic payoff for the Texas senator’s presidential campaign.

Behind the scenes, Cruz has been methodologically developing Trump’s support. The two candidates have met in person at least five times and talk by phone occasionally. And in the future, they may even hold events together.

The two campaigns privately discussed a possible joint event this year in Washington, D.C., and Cruz was invited to join Trump’s infamous trip to the Mexico border, though a scheduling problem prevented him from attending, sources told The Daily Beast.

“In terms of Trump’s civility, if you’re nice to him, he’ll be nice to you. And Cruz has been nice. Cruz is playing the long game and hopes that if he survives and Trump doesn’t, the billionaire will swing to him. He’s the second choice for a lot of Trump voters,” said a source familiar with the inner workings of the Trump campaign.