AP
The Republican formally announced his departure in Maryland during an address at the Conservative Political Action Conference.
"Even though I might be leaving the campaign trail - you know there's a lot of people who love me, they just won't vote for me," he said.
"I will still be heavily involved in trying to save our nation," he added.
After making his announcement, he answered questions in a somewhat lighthearted manner from Fox News contributor Mercedes Schlapp.
During that session, he said that after adding up the needed delegates and realizing that it would be impossible for him to win, he decided to drop out so as not to "interfere with the process."
He did not endorse one of the four remaining GOP candidates.
Now that he's out of the race, Carson is taking a new job. He will serve as chairman of My Faith Votes, an organization that works on getting Christian Americans to vote.
Carson announced on Wednesday that he would not participate in the primary debate the next day. The decision came after a disastrous Super Tuesday, in which he failed to finish better than fourth in at least 11 of the 12 Republican primary or caucus states that voted that day.
He said at the time that he did not see a "path forward" in his bid for the presidency. That tone differed greatly from his rhetoric following the Super Tuesday primaries.
In a speech to supporters on Tuesday evening, Carson said that he was "not ready to quit." But even people closest to Carson said publicly that he had no chance of winning, seeming to give up before the one-time frontrunner was ready to call it quits.
"I've always said that March 2 was D-Day," Armstrong Williams, Carson's longtime business manager who was not officially affiliated with the campaign, told Business Insider on Wednesday.
He continued: "I think they were hoping that from Iowa to New Hampshire to South Carolina the voters would" show the campaign that there is a pathway forward to the nomination.
But "it did not happen," he said.
With Carson failing to win any state primaries or caucuses, "there isn't much to argue with," Williams said.
Bob Dees, Carson's campaign chair, also told the Washington Examiner on Tuesday that the campaign doesn't know how to win and that "we don't have a well-defined path to victory."