“Unfortunately,” the statement added, “Senator Cruz has chosen to remain in his bunk below, a decision both regrettable and revealing.”

The Mercers invested at least $11 million in Keep the Promise I, one of a group of interlocked “super PACs” that supported Mr. Cruz in his presidential run. During the contentious primary race, Mr. Cruz had early praise for Mr. Trump on the belief that his candidacy would eventually fade and that Mr. Trump’s voters would move over to the senator’s camp.

Instead, Mr. Trump’s candidacy endured and the race between the men grew increasingly rancorous.

Mr. Cruz is up for re-election in 2018 and is said to be looking at a second campaign for president in 2020, should Mr. Trump lose in November. But, in both cases, he will need his donor base to stay with him.

After Mr. Cruz’s speech at the convention in Cleveland, Sheldon G. Adelson, the casino magnate who was an early admirer of Mr. Cruz in the primaries, blocked him from his suite. (A friend of Mr. Adelson’s, claiming to represent him, insisted after the fact that he was not trying to disrespect the senator.)

The next morning, Mr. Cruz was booed by members of the Texas delegation at a breakfast.

A spokeswoman for Mr. Cruz, Catherine Frazier, said on Saturday: “Senator Cruz considers Bob and Rebekah to be patriots and friends. As Senator Cruz urged in Cleveland, Hillary Clinton would be a disaster for America. Republicans need to unite, and the only way to unite is behind shared principles. His speech laid out a path — vigorously defending freedom and the Constitution — for our nominee to unite the party and for Republicans to win up and down the ticket.”