U.S. Senator Ted Cruz (R-TX) (R) greets businessman Donald Trump onstage as they address a Tea Party rally against the Iran nuclear deal at the U.S. Capitol in Washington September 9, 2015. Both Cruz and Trump are U.S. Republican presidential candidates. REUTERS/Jonathan Ernst - RTSD93

A supporter holds up a sign with an error as U.S. Republican presidential candidate Ted Cruz speaks at a campaign event in Syracuse, New York April 15, 2016. REUTERS/Carlo Allegri - RTX2A6I1

Jim Stryker, of San Francisco, holds a sign in protest of Republican U.S. presidential candidate Ted Cruz during the California GOP convention in Burlingame, California, U.S., April 30, 2016. REUTERS/Stephen Lam - RTX2C9EG

Protesters stand outside the Town & Country Resort where Republican presidential candidate Ted Cruz is speaking at a rally in San Diego, California, United States, April 11, 2016. REUTERS/Mike Blake - RTX29ITU

A delegate holds a sign that call for Ted Cruz delegates to support Donald Trump at the Republican National Convention in Cleveland, Ohio, U.S. July 20, 2016. REUTERS/Jim Young - RTSIY13

Republican U.S. presidential candidate Ted Cruz gestures over at rival candidate Donald Trump (L) at the U.S. Republican presidential candidates debate in Detroit, Michigan, March 3, 2016. REUTERS/Jim Young - RTS97R3

A delegate carries a sign referring to Texas Senator Ted Cruz at the Republican National Convention in Cleveland, Ohio, U.S. July 21, 2016. REUTERS/Jim Young - RTSJ3UP

Republican U.S. presidential candidate Ted Cruz challenges rival Donald Trump (L) about releasing his tax returns during the debate sponsored by CNN for the 2016 Republican U.S. presidential candidates in Houston, Texas, February 25, 2016. REUTERS/Mike Stone - RTX28N9Q

Republican U.S. presidential candidates Donald Trump (L) and Ted Cruz shake hands at the start of the Republican candidates debate sponsored by CNN at the University of Miami in Miami, Florida, March 10, 2016. REUTERS/Joe Skipper - RTSA9ZS

Heidi Cruz, wife of Republican U.S. presidential candidate Senator Ted Cruz, bites her lip and closes her eyes as she listens to her husband drop out of the race for the 2016 Republican presidential nomination during his Indiana primary night rally in Indianapolis, Indiana, U.S., May 3, 2016. REUTERS/Chris Bergin - RTX2CPKP

Republican U.S. presidential candidate Donald Trump (L) talks with rival candidate Ted Cruz during a commercial break in the midst of the Republican U.S. presidential candidates debate sponsored by CNN at the University of Miami in Miami, Florida March 10, 2016. REUTERS/Carlo Allegri - RTSAA3K

Former Republican U.S. presidential candidate and Texas Senator Ted Cruz speaks during the third session of the Republican National Convention in Cleveland, Ohio, U.S. July 20, 2016. REUTERS/Rick Wilking - RTSIY7I

U.S. Republican presidential candidate Ted Cruz (R-TX) speaks with supporters of fellow candidate Donald Trump during a campaign event at The Mill in Marion, Indiana, U.S., May 2, 2016. REUTERS/Aaron P. Bernstein - RTX2CHFI

Republican U.S. presidential candidate Donald Trump shows off the size of his hands as rivals Marco Rubio (L), Ted Cruz (2nd R) and John Kasich (R) look on at the start of the U.S. Republican presidential candidates debate in Detroit, Michigan, U.S., March 3, 2016. REUTERS/Jim Young/File Photo - RTSOX8N

Republican U.S. presidential candidates Donald Trump (L) and Ted Cruz (R) speak at the debate sponsored by CNN for the 2016 Republican U.S. presidential candidates in Houston, Texas, February 25, 2016. REUTERS/Mike Stone - RTX28NDY