In a matter of 72 hours, Joe Biden parlayed a dominant victory in South Carolina into a steamrolling performance on Super Tuesday: He not only won substantially African American electorates like Alabama's and Virginia's, but he also carried Texas and scored huge coups by winning Massachusetts, Minnesota and Maine — all states thought to be favorable to Bernie Sanders.

And Biden did so without much of a personal, TV or field presence in any of them.

According to the latest NBC News projection, Biden leads Sanders by 513 to 461 in pledged delegates, with 105 for other candidates (1,991 are required to win the nomination). There are still millions of votes to count in California in the coming days, giving Sanders room to grow. But Biden's total will also grow as his best states are certified and delegates are awarded based on the results calculated in each congressional district.

Here are three reasons the former vice president is amassing what could be an insurmountable delegate lead.

Super Tuesday resurrected Joe Biden’s campaign and powered him into a delegate lead. Super Tuesday II must revive Bernie Sanders or the nomination could slip away from him again.

A new CNN poll shows Biden leading Sanders by a margin of 52 percent to 36 percent in a two-person race. The biggest dividing line is age — voters under 45 said they prefer Sanders by nearly 2-to-1, while voters 45 or older picked Biden by more than 4-to-1.

That generational gap looms over another big day of voting Tuesday, with Democratic voters in Michigan, Idaho, Mississippi, Missouri, North Dakota and Washington set to deliver their verdict on who the party’s nominee to take on President Donald Trump should be. It’s also the last day for Democrats living abroad to participate in the primary.

Here are five things to watch on Super Tuesday II.

The six states voting in the primaries and caucuses Tuesday are bracing for a strong turnout after some voters in California and Texas waited hours in long lines to cast their ballots.

Election officials and experts are hoping that with less new technology, more paper-based methods and early and absentee voting options, the states — Idaho, Michigan, Mississippi, Missouri, Washington, and North Dakota — have fewer bottlenecks. But other changes may delay reporting of the results.

“We do not anticipate unusually long lines in the March 10 states, primarily due to variables such as voting methods, state sizes and the absence of major process changes such as the introduction of Vote Centers,” Eddie Perez, an election administration analyst with the technology group OSET Institute, said in an email.

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WASHINGTON — It may not be super, but as the Democratic race hits the latest round of contests today, Joe Biden is looking to replicate his strong showing on last week's Super Tuesday and widen his delegate lead over Bernie Sanders. 

The Sanders campaign is outspending Biden on the TV and radio airwaves across the six states that hold their nominating contests today — $2.9 million to Biden's almost $2.2 million, according to Advertising Analytics. But Biden's effort has been boosted by spending from his allied super PAC, Unite the Country. 

Both campaigns are spending the most in Michigan — Sanders and Biden have spent about $1.2 million each, with Unite the Country spending another almost $400,000.  

The Biden campaign and his super PAC have also run ads in Missouri and Mississippi, but neither have spent a cent on TV or radio ads in Washington, Idaho and North Dakota.

The Sanders campaign, by comparison, has gone up on the airwaves in all six states voting Tuesday. 

Sanders' top ad across these states, according to Advertising Analytics data, is one that attacks Biden on social security by using audio from a speech in 1995 where he called for a spending freeze across the government. His campaign has spent more than $644,000 to air the ad in states holding votes on Tuesday. 

The Biden campaign has bristled at those attacks, and has spent almost $200,000 in those states on ads that criticize Sanders for going negative and argue Biden has said he'd expand Medicare and Social Security. 

Biden's top ads in the states voting Tuesday are different versions of the same spot, which feature former President Obama's praise of Biden as "an extraordinary man with an extraordinary career in public service." 

And Unite Our Country has spent $376,000 in these states on a spot that quotes Biden talking about his campaign, and includes some brief swipes at Sanders (Biden is quoted int he ad saying he wants to "build on ObamaCare" instead of scrapping it, and "Democrats want a nominee who is a Democrat"). 

Four years ago, Bernie Sanders shocked the political world and defied the public polling by winning the Michigan primary — even though he was unable to change the overall delegate math.

But here are three reasons why Sanders winning Michigan tonight on this Above-Average Tuesday would be an even bigger surprise than it was in 2016.

Missouri has experienced minor technical issues as its primary election is underway.

Kansas City Mayor Quinton Lucas tweeted a video that he had been turned away at the polls this morning. "I wasn’t in the system even though I’ve voted there for 11 years, including for myself four times!" he wrote.

But that was the result of a simple user error, Missouri Secretary of State Jay Ashcroft told NBC News.

"He's in the system. He's registered. He has been registered. The poll worker misspelled his name," Ashcroft said.

Missouri does not require voters to present identification when voting, but Ashcroft said he recommended voters present them to avoid misspellings.

Other voters reported glitches that prevented them from voting normally.

Adam Rygiol, 34, said that even though registration tablets at his polling location in Jackson County, MO, recognized he was eligible to vote, he and another man couldn't complete their ballot normally, and had to sign provisional ballots.

"My understanding is that some of those tablets were not communicating with each other between 6:00 and 6:30" in Jackson and St. Louis Counties, Ashcroft said, but that affected voters could vote provisionally, and that the problem had since been resolved.