In a remarkable rebound for his campaign, Joe Biden has won nine of the 14 states that voted to pick a Democratic White House candidate on Super Tuesday.
The former vice-president to Barack Obama overturned predictions to narrowly take the key state of Texas from his main challenger, Bernie Sanders.
However, Bernie Sanders is projected to win California – the biggest prize of the night – as well as three other states.
Joe Biden and Bernie Sanders lead the race to face Republican President Donald Trump in November.
Former New York Mayor Michael Bloomberg spent more than $500 million of his own money on his campaign, but did not win a single state.
Senator Elizabeth Warren, once the frontrunner in the race, suffered a humiliating defeat to Joe Biden in her home state of Massachusetts.
Super Tuesday awards more than 1,300 of the 1,991 delegates needed to clinch the Democratic White House nomination in July.
As things stand, Joe Biden has 402 delegates and Bernie Sanders 314. However, results from California, which has 415 delegates, could affect the current standing.
Only last month, Joe Biden’s campaign was all but written off by some observers after he finished a poor fourth in the Iowa caucuses and fifth in the New Hampshire primary.
Joe Biden won Texas – the second biggest state with 228 delegates – along with Massachusetts, Minnesota, Oklahoma, Arkansas, Alabama, Tennessee, North Carolina and Virginia.
Maine, which has 24 delegates, is also yet to declare but partial results put Joe Biden slightly ahead of Bernie Sanders.
Virginia and North Carolina are crucial because they are key swing states in the 2020 election.
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Exit polls across the board suggested Joe Biden attracted large majorities of African-American voters, a crucial bloc for the Democratic Party.
Joe Biden, 77, also appears to have won among the type of suburban voters who pollsters say have been turning away from the current president.
If Bernie Sanders, 78, does win California, as the Associated Press news agency projects, he will pick up the lion’s share of the whopping 415 delegates that the Golden State sends to the party convention.
The left-wing senator also won his home state of Vermont, along with Colorado and Utah.
Bernie Sanders had been heavily favored to win Texas, but it was finally claimed by Joe Biden.
In a victory speech, Bernie Sanders lambasted President Trump, but also took a shot at Joe Biden.
He said: “We’re taking on the political establishment.
“You cannot beat Trump with the same-old, same-old kind of politics.”
The next primaries take place on March 0 in Michigan, Washington state, Idaho, Mississippi, Missouri and North Dakota, with 352 delegates available.