But Wednesday night, Cruz refused and instead said, "vote your conscience."
This was supposed to be Mike Pence's night at the Republican National Convention in Cleveland, but the GOP nominee for vice president was overshadowed by a stunning moment earlier in the night. The appearance of Cruz. All 17 Republicans candidates took a pledge to support the eventual nominee, but did Cruz live up to that promise?
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"Unlike Hillary Clinton, Donald Trump is committed to cutting taxes," Marco Rubio said.
In hindsight, it might've been better for Ted Cruz to go the Marco Rubio route and appear at the RNC in Cleveland by video.
"Stand and speak and vote your conscious and vote for candidates that you trust up and down the ticket that you trust," Cruz said.
Instead, Cruz stood before a party that's now nominated Trump and steadfastly refused to endorse their candidate, even in the face of a loud chorus of chants and boos.
"We will defend freedom and defend and be faithful to the constitution," Cruz said.
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In the end, Cruz was booed off the stage just as Trump walked into the arena. At the same time, Cruz's wife Heidi had to be escorted from the building due to verbal threats.
"Honestly, if he wants the Trump supporters for a future run, that wasn't the right way to get them," said California delegate Brian Wallace.
Wow, Ted Cruz got booed off the stage, didn't honor the pledge! I saw his speech two hours early but let him speak anyway. No big deal!— Donald J. Trump (@realDonaldTrump) July 21, 2016
"He signed a pledge and his word isn't worth much and I think his career is over," said California delegate Sharon Carter.
For his part, vice-presidential nominee Mike Pence did exactly what he was expected to do, attack Hillary Clinton and make a passionate case for Trump.
"I am deeply humbled by your confidence." Pence said. "And when we elect Donald Trump the 45th president of the United States, together we will make America great again."
Donald Trump joined Pence on the stage, for his third appearance at the RNC. Trump is expected to give his acceptance speech Thursday night.
ABC7 anchor Reggie Aqui and reporter Laura Anthony are reporting live from the RNC in Ohio. You can follow them on social media: Click here to follow Reggie on Facebook and click here for Twitter. Track Laura Anthony on Facebook here and follow her Twitter here.
For full coverage of the 2016 RNC, click here, and click here for full coverage on the presidential race.