In a Facebook message posted on Friday, Senator Ted Cruz announced his endorsement of his former foe, Republican presidential candidate, Donald Trump.

This directly contradicts his unpopular refusal to support Trump at the Republican National Convention in July. Cruz’s speech at the convention was booed and the disagreement got personal. The primary campaign leading up to the convention saw personal attacks being made back and forth between the two. Cruz accused Trump of verbally attacking his wife, Heidi, and his father, Rafael. Trump responded by saying he would not accept Cruz’s endorsement if it was offered.

In his announcement, Cruz cited two reasons for deciding to support his former nemesis: His promise at the convention to support the party’s candidate, and a victory by Democratic candidate Hillary Clinton being “wholly unacceptable”.

“If Clinton wins, we know — with 100% certainty — that she would deliver on her left-wing promises, with devastating results for our country,” Cruz wrote in his Facebook statement. “My conscience tells me I must do whatever I can to stop that.”

Trump made a statement to the press on Friday, thanking Cruz for the endorsement.

“I am greatly honored by the endorsement of Senator Cruz,” the statement said. “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.”

The @SenTedCruz endorsement was a wonderful surprise. I greatly appreciate his support! We will have a tremendous victory on November 8th.

— Donald J. Trump (@realDonaldTrump) September 24, 2016