Rand Paul, a US senator from Kentucky with a libertarian philosophy, pulled out of the Republican race. Conservative Rick Santorum also exited the race on Wednesday and endorsed US Senator Marco Rubio of Florida.
Both Paul and Santorum, a former senator from Pennsylvania, did poorly in Monday's Iowa caucuses, which were won by Cruz, with Trump and Rubio finishing second and third. The caucuses were the first of the state-by-state nominating contests ahead of the 8 November election to replace Democratic President Barack Obama.
