Marco Rubio has dropped out of the US presidential race and congratulated Donald Trump on his victory in Florida, Mr Rubio's home state.
With 83 percent of the vote counted, the controversial frontrunner for the Republican presidential nomination is on 47 percent. Mr Rubio -- who has criticised Mr Trump as an "embarrassment" to the party -- was on 27 percent.
"It is clear while we are on the right side, this year we will not be on the winning side," he told supporters during his concession speech, which was interrupted by a supporter of Mr Trump yelling, "Trump for president."
Ted Cruz was on 17 percent and John Kasich, perhaps the most moderate of the remaining candidates, 7 percent. Ben Carson, who has already dropped out of the race, was on 1 percent.
"The politics of resentment against other people will not just leave us a fractured party...but will leave us a fractured nation," Mr Rubio said.
Mr Rubio had been increasingly strong in his opposition to Mr Trump, but today admitted his presidency was "not in God's plan".
"In their hearts, humans plan their course; but the Lord establishes their steps."
Mr Rubio had earlier claimed he would continue campaigning even if he lost Florida, desperate to prevent Mr Trump from winning the nomination.
"People around the world are watching this debate and this campaign and wondering what's happening here, because the things he says are nonsensical," he told UK newspaper The Guardian yesterday.
"When you're the most powerful and important nation on Earth, you're not always going to be popular. But the question is, are you respected? And I don't think Donald Trump is going to be respected."
Meanwhile in Ohio, Mr Kasich is edging ahead of Mr Trump, leading 44-32 in early counting, while in North Carolina, early counting has Mr Trump pipping Mr Cruz by a few percentage points.
Mr Cruz told a radio station earlier he has "zero interest" in being Mr Trump's running mate, and still believes he can win.
Early counting on the Democrat side had Hillary Clinton well ahead of Bernie Sanders in Ohio, Florida, Missouri and North Carolina. In a speech, delivered from Florida, the former First Lady took aim at Mr Trump's plan to ban Muslims from entering the US.
"It doesn't make him strong -- it makes him wrong."
Before today, Mr Trump led the Republican race with 469 delegates secured, out of a total 1237 to be guaranteed the nomination. Mr Cruz had 370, Mr Rubio 163 and Mr Kasich, 63.