American Carnage: On the Front Lines of the Republican Civil War and the Rise of President Trump by Tim Alberta:
By early March, with Trump clearing 40 percent in multiple nominating contests, it was clear that something radical needed to happen, and quickly, to prevent him from running away with the nomination. That's when an idea took root among Cruz's staff: a ticket with Rubio. The Florida senator was treading water and heading for a certain exit after losing Florida; what would happen if he teamed up with Cruz, running as his vice-presidential-pick-in-waiting?
Cruz was lukewarm to the idea. The two senators had a strained relationship, and the last several months, including Rubio's jab about not speaking Spanish, had been especially spiteful. But his outlook brightened upon seeing the polling. According to number compiled by Cruz's gold-standard data analytics team, a Cruz-Rubio ticket would demolish Trump in head-to-head competition in the remaining primaries, often winning more than 60 percent of the vote.
Cruz's pollster, Chris Wilson, called Utah senator Mike Lee to share the campaign's findings. Lee had not endorsed in the primary; he was close friends with both Cruz and Rubio. Reviewing the data, Lee sprang into action. He called dozens of hotels in the Miami area, needing one with an underground parking garage and an elevator that could ferry guests directly up to a private suite. Upon securing such an arrangement, at the Hilton Miami Downtown, Lee called Rubio to set up a meeting for March 9, one day before the Republican debate in nearby Coral Gables. He then informed Cruz that Rubio had agreed to a secretive sit-down at five o'clock that afternoon. Cruz cleared his campaign schedule and held his breath.