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WATCH: PBS NewsHour’s Super Tuesday special coverage

WASHINGTON (AP) — The Democratic presidential race is about to floor the accelerator.

Super Tuesday is here and up for grabs are more than one-third of the delegates needed to win the nomination. The entire complexion of the race will change with the 1,344 delegates that will be won in 14 states and American Samoa.

Watch PBS NewsHour’s special coverage of Super Tuesday in the video player above.

The fight to take on Donald Trump is about collecting the 1,991 delegates needed to win, and Tuesday is the biggest day on the delegate calendar. By far.

“Super Tuesday is where the delegate counts begin to be meaningful,” said University of Arizona political scientist Barbara Norrander. “It’s also where candidates who lag behind in delegate totals will drop out. Sometimes one candidate develops a lead with Super Tuesday that other candidates cannot catch up with. In 2016, Super Tuesday was where (Hillary) Clinton developed her lead in pledged delegates. In some years the race is essentially over (after) Super Tuesday.”

Until now, Democrats have won 155 delegates. But on Tuesday, Democrats are picking nearly nine times as many delegates. Vermont Senator Bernie Sanders’ leading total of 60 delegates is smaller than the prizes in California (415), Texas (228), North Carolina (116), Virginia (99), Massachusetts (91), Minnesota (75), Colorado (67) and Tennessee (64).

MORE: Super Tuesday’s full election results

Here’s where the other active candidates are now, coming out of Iowa, New Hampshire, Nevada and South Carolina: former Vice President Joe Biden has 54 and Senator Elizabeth Warren has eight. Sen. Amy Klobuchar, who has seven delegates, suspended her campaign on Monday.

“I would expect the front-runner to be somewhere in the range of 400 – 500 delegates after Super Tuesday,” said Virginia Tech political scientist Caitlin Jewitt. “If a candidate has more than 700 delegates after the Super Tuesday states vote, and the next candidate is far behind, that would be evidence that he or she is a strong front-runner.”

Super Tuesday is so huge that it can’t be contained in one day.

Voting was scheduled to start in Bangkok, Thailand, which is part of the worldwide Democrats Abroad primary, at 11 a.m. local time, still Monday evening in the United States. American Samoa’s caucus is likely to be the first results reported and delegates won.

More than 3 million Democrats in the 14 Super Tuesday states have already voted early, either in person or by absentee.

And the results won’t be too clear until Wednesday at the earliest. California’s polls close at 11 p.m. Eastern time and the country’s largest state traditionally does not count a huge portion of its vote by the end of election night. In 2018, nearly 44% percent of California’s ballots weren’t counted on election night.

Add to that the fact that 65% of the 1,344 votes at stake Tuesday are from congressional districts, not statewide. Because some states don’t separate vote totals quickly by congressional districts, the overall delegate totals may take a few days to be final.

And the Democrats Abroad primary that starts Tuesday goes on for a week and won’t be reported until March 23.

In the past, Super Tuesday also got nicknamed the SEC primary because it was so oriented toward southern states. It’s still heavily southern — 45% of the delegates are chosen from states south of the Mason-Dixon line — but it is balanced by California’s 415 delegates as the Golden State moves into the big day for the first time.

“Adding California to the mix dilutes southern influence,” said political scientist Josh Putnam, who runs the delegate-oriented website Frontloading HQ.

And California is huge.

“Winning California by a large margin will be most helpful to a candidate looking to establish a delegate lead,” Jewitt said.

Associated Press reporter Seth Borenstein wrote this story. The PBS NewsHour produced the video.