Michael Bloomberg has announced his decision to drop out of the 2020 presidential race.
“Three months ago, I entered the race for president to defeat Donald Trump. Today, I am leaving the race for the same reason,” he said in a statement.
Mr Bloomberg, a former mayor of New York City, has spent more than $500m (£390m) of his own money in the race to become the Democratic Party’s nominee.
He said he would now support former Vice-President Joe Biden.
“I’ve always believed that defeating Donald Trump starts with uniting behind the candidate with the best shot to do it. After yesterday’s vote, it is clear that candidate is my friend and a great American, Joe Biden,” Mr Bloomberg said in his statement.
Out of the 14 states and territories which voted on Tuesday, the billionaire only managed to win in American Samoa.
Joe Biden won nine of the states, a remarkable rebound for his campaign.
The former US vice-president overturned predictions to narrowly take the key state of Texas from his main challenger, Bernie Sanders.