Immediately following Cruz's speech, a series of party leaders -- both Trump loyalists and reluctant supporters -- slammed the Texas firebrand for his non-endorsement, in which he told the audience to "vote their conscience."
The Republican presidential nominee himself tweeted
shortly after Cruz's speech, writing, "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!"
In an interview with CNN's Dana Bash, New Jersey Gov. Chris Christie -- among the first of Trump's major Republican primary opponents to endorse him -- said he thought Cruz's speech was "awful" and "selfish." He criticized Cruz for reneging on a pledge signed by all GOP presidential candidates through which they vowed to support the eventual nominee.
"He signed the pledge. And it's his job to keep his word. And Donald Trump gave him the opportunity to speak here at this convention tonight, and I think it was too cute, and I think you saw by the end of the speech that the crowd was waiting for him to do the right thing, and realized that once again he wasn't going to do it," Christie said.
He added, "And I think the performance you saw up there is why Ted has so richly deserved the reputation he's developed on Capitol Hill."
Michael Cohen, special counsel to Trump, praised his boss and called the nominee's former rival "a baby."
"Donald J. Trump is bigger than Ted Cruz, it just goes to show the distinction between an adult and a baby, and a baby that happens to be a sore loser," he told Chris Cuomo on CNN's "New Day."
Newt Gingrich, the former House speaker who was at one point a leading contender to be Trump's vice president pick, was more sanguine. He thought that what Cruz said -- even without an explicit endorsement -- more or less amounted to an expression of support. Still, Gingrich said he wasn't surprised by the boos.
"When he said in his speech that you could vote your conscience as long as it was for somebody who supported the Constitution, that by definition meant you're not talking about Hillary Clinton," Gingrich told CNN. He added, though, that "these are people who want Donald Trump to be elected president and I think you're sort of asking for boos if you show up without endorsing."
But New York Rep. Peter King -- who has been a regular critic of Cruz -- issued one of the sharpest rebukes.
"Tonight, America saw the real Ted Cruz. He's a fraud, he's a self-centered liar and should be disqualified from ever being considered as a nominee for President of the United States in the future," King said in an interview with CNN. "I never liked the guy, never trusted him but tonight was the worst. To take the time at a national convention and not endorse the nominee is disgraceful."
Asked about a convention delegate who had reportedly called Cruz an "a--hole," King replied: "That's not far enough."
When asked about King's comment, Republican National Committee communications director Sean Spicer told CNN, "I'd probably use the same verbiage."
Arizona Rep. Trent Franks, a supporter of Cruz during the primary, said he was "disappointed" by the speech, adding that "for the people in this room, a vote of conscience is a Trump vote."
And Michigan Rep. Bill Huizenga, who initially supported Florida Sen. Rubio, was also displeased, calling the speech "a mistake." He said Cruz should have followed the example of Ronald Reagan at the 1976 convention, who he said "went on to live to fight another day."
Virginia State Sen. Richard Black said he was "disappointed" in an interview with CNN.
"I'm disappointed because the election for Presidency is more than about an individual, it is about the nation and I think all of the Cruz voters were looking for a message to the nation," he said, "not a message about an individual."
Wisconsin Gov. Scott Walker, one of Cruz and Trump's 2016 rivals, fully endorsed Trump in his speech, but declined to criticize the Texas senator for his non-endorsement. Asked multiple times what he thought about Cruz's speech, Walker replied, "I think my speech was great; I love talking about how America deserves better." Eventually, he conceded, "It was the year of the unexpected."
Rep. Chris Collins, one of the first members of Congress to endorse Trump, called Cruz's move "typical."
"First of all it made him a small person and it's typical Ted Cruz -- all about him. But I'd like to maybe remind Ted, America did vote their conscious. They didn't vote for him," the New York Republican told CNN's Alisyn Camerota Wednesday on "New Day."
"This is just plain rude but it's Ted Cruz. He's all about himself, which is why he's got no friends in Washington, D.C. except to a few Tea Party extremists."
Rick Perry eventually endorsed Cruz after ending his own presidential bid. But the former Texas governor also told CNN Thursday that Cruz should have "kept his word" and endorsed Trump.
"At the end of the day, we all made a pledge that we were going to support our nominee. And if you don't want to keep your word then don't be signing pledges," he said.
"I think it was a bad call from my perspective."
Eric Trump, who also spoke last night, highlighted the opposition to Cruz's words.
"How do you get booed out of your own convention. ... By your own party? And by your own delegation," he asked Thursday on CBS' "This Morning." "It was unbelievable."
Trump, the Republican nominee's son, called Cruz's words "classless."
"I thought it was classless, to tell you the truth," he said. "If you're going to go to convention you either go to support or you just don't go at all. It's Politician 101."