Ben Carson will endorse his former rival Donald Trump on Friday, the real estate mogul announced during Thursday evening's debate.

The Washington Post first reported Carson's endorsement. Trump has scheduled a 9 a.m. ET press conference at his Mar-a-Lago Club resort in Palm Beach, Fla., where the retired neurosurgeon is expected to make his endorsement official.

Carson's support comes just a week after he officially ended his campaign. The famed African-American physician had a surge of support last fall, but faltered after his comments regarding terrorist attacks exposed his weaknesses on foreign policy.

The conservative favorite could help boost Trump heading into a critical primary day on Tuesday, where big winner-take-all prizes are up for grabs in Florida and Ohio.

The relationship between the two hasn't always been warm and fuzzy. Late last year as Carson was on the rise, Trump came out swinging at him, questioning the redemption story at the heart of Carson's narrative — how he overcame a violent childhood and a "pathological temper" to become a world-renowned surgeon.

"If you're a child molester, there's no cure. They can't stop you. Pathological? There's no cure," Trump said.

Carson's animosity for Ted Cruz may have run deeper, though. On the night of the Iowa caucuses, Carson criticized the Texas senator for circulating a press report suggesting Carson was preparing to drop out of the race.

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