"After many months of careful consideration, of prayer and searching my own conscience, I have decided that on Election Day, I will vote for the Republican nominee, Donald Trump," wrote Cruz.
The question of whether Cruz, the Republican primary's second-place finisher, would cast a ballot for the party's nominee had been in question, particularly after he gave a fiery speech at the Republican National Convention in July.
Speaking on the third night of the RNC, Cruz encouraged conservatives to "vote your conscience" and never specifically endorsed Trump, who had overcome a last-ditch effort by Cruz supporters to secure the nomination on the convention's first day.
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Trump responded to Cruz the day after the Texas lawmaker's address, calling the senator “dishonorable” for rejecting the pledge Republican candidates signed during the primaries indicating they would support the party's eventual nominee.
Today, Cruz said that he is embracing that pledge.
"A year ago, I pledged to endorse the Republican nominee, and I am honoring that commitment," wrote Cruz on Facebook.
But on the morning following Cruz's speech to the RNC, the senator said that the pledge was not "a blanket commitment."
"I am not in the habit of supporting people who attack my wife and attack my father," said Cruz at a breakfast for the Texas delegation. "And that pledge was not a blanket commitment that if you go and slander and attack Heidi, that I’m going to nonetheless come like a servile puppy dog and say 'thank you very much for maligning my wife and maligning my father.'"
That same day, Trump made clear that he would neither seek nor accept an eventual endorsement from Cruz.
"I like Ted, he's fine. Again, don't want his endorsement," Trump said. "If he gives it, I will not accept it, just so you understand."
Friday afternoon, Trump released a statement in response to the news, saying he is "greatly honored by the endorsement of Senator Cruz."
"We have fought the battle and he was a tough and brilliant opponent. I look forward to working with him for many years to come in order to make America great again," reads the statement.
Among the 17 primary candidates for the Republican nomination, former Florida Gov. Jeb Bush, Ohio Gov. John Kasich, South Carolina Sen. Lindsey Graham and former New York Gov. George Pataki have all withheld their support from Trump.
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ABC's Jessica Hopper and Katherine Faulders contributed to this report.