Joe Biden Joe BidenMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE continued his once-improbable march to the Democratic presidential nomination Tuesday, trouncing Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.) in major primaries, with a decent turnout despite the coronavirus pandemic.

A landslide in Florida, with the third-most Democratic convention delegates, and a decisive victory in Illinois, with the sixth-largest bloc, gives the former vice president a delegate lead of more than 300, and he'll rack up even more with a clear win in Arizona — a clean sweep.

Because of the deadly pandemic, Ohio called off its presidential primary yesterday, and the Georgia contest next week also has been postponed. In that context, turnout was surprisingly high in Florida and Arizona. This reflects the intensity Democrats feel this year.

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It is virtually impossible for Sanders to catch Biden now, regardless of when primaries are held. The Vermont socialist will likely now focus on pressuring Biden and the party to move left.

Barack Obama Barack Hussein ObamaMomentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina Majority of voters say Trump should not nominate a Supreme Court justice: poll MORE's vice president will have to delicately handle his appeal to the Sanders wing while not turning off independent-minded voters who want to get rid of Trump.

But wrapping up the nod this early makes the task easier.

The Biden turnaround, going from front-runner a year ago to a failed candidacy a month ago, to inevitable nominee today, is unprecedented in American politics.

Every rule I learned in covering presidential politics for almost a half century has been broken, including:

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No one loses both Iowa and New Hampshire and wins the nomination. An also-ran in these first contests loses momentum, money and political support. Serious contenders failed miserably to jump start campaigns. For the Democrats in 1976, Sen. Henry Jackson skipped New Hampshire — and when Jimmy Carter Jimmy CarterWarning signs flash for Lindsey Graham in South Carolina Jimmy Carter remembers Ruth Bader Ginsburg as 'a beacon of justice' With 5 weeks to go, the economy and Trump are surging MORE won the Granite State, it effectively ended Jackson's hopes. In 2008, the early Republican front-runner Rudy Giuliani Rudy GiulianiGrand jury adds additional counts against Giuliani associates Lev Parnas and and Igor Fruman Juan Williams: Breaking down the debates Giuliani criticizes NYC leadership: 'They're killing this city' MORE — really he once was a serious person — figured he'd take off in the big Florida primary. But after John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE won New Hampshire, support for “America’s Mayor” plummeted; he dropped out nine days before the Florida primary. Biden, however, finished fourth in Iowa, fifth in New Hampshire and is now on his way to November.

Endorsements don’t really matter in the modern media age. Witness the last two presidents. In 2007, the establishment candidate, Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE, cornered scores of high-level endorsements — far more than Barack Obama — to little avail. Four years ago, about the only top Republican to endorse Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE was Alabama Sen. Jeff Sessions Jefferson (Jeff) Beauregard SessionsTrump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status White House officials voted by show of hands on 2018 family separations: report MORE. (The president showed his sense of loyalty this month by endorsing Sessions' opponent in a primary.) Then there was Jim Clyburn James (Jim) Enos ClyburnAzar to testify before House coronavirus subcommittee Attacks against the police are organized and violent Clark rolls out endorsements in assistant Speaker race MORE. Joe Biden might have won the South Carolina primary last month anyway — but the eloquent endorsement of Rep. Clyburn, the most important African American office holder in the party, generated the Biden avalanche in South Carolina, carrying over to Super Tuesday three days later.

Money is the mother's milk of politics, especially if one candidate has a lot, the other very little. By Super Tuesday, Mike Bloomberg was spending more than a half a billion dollars, while Biden was too strapped to even have offices in some of the states in play. Biden won 10 of 14 states that day, picking up 632 delegates. Bloomberg won American Somoa. The “Big Mo” triumphed — momentum not money.

Democrats — in a change election — turn to younger, outside-the-Beltway candidates. Think Jimmy Carter, Bill Clinton William (Bill) Jefferson ClintonDolly Parton remembers Ginsburg: 'Her voice was soft but her message rang loud' Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Calls grow for Biden to expand election map in final sprint MORE, Barack Obama. They conveyed change, a new day. This time, the party is turning to a 77-year-old who was first elected to the Senate before any of the current members of Congress arrived.

The answer lies in Democratic voters who passionately want change — to defeat the incumbent.

They've come to see Biden as the antidote to Trump: honorable, experienced, sound and decent.

Al Hunt is the former executive editor of Bloomberg News. He previously served as reporter, bureau chief and Washington editor for the Wall Street Journal. For almost a quarter century he wrote a column on politics for The Wall Street Journal, then the International New York Times and Bloomberg View. Follow him on Twitter @AlHuntDC.