In recent decades, old-style kingmakers faded from American politics. This year, though, there are hundreds of thousands of them: the African American voters across the South who gave Joe Biden a lead in the race for the Democratic nomination.

Kingmaker in chief is House Majority Whip James E. Clyburn (D-S.C.), whose emotional, full-throated endorsement last week lifted Biden to a landslide in a state where black voters make up more than half of the Democratic electorate. After Clyburn weighed in, what had been a confusing picture — Would younger African Americans turn out in droves for Sen. Bernie Sanders (I-Vt.)? Was billionaire Tom Steyer’s barrage of television ads across the state winning him votes? — suddenly became crystal clear.

Biden ended up winning 61 percent of the black vote in South Carolina, according to exit polls. But what happened three days later, on Super Tuesday, was even more impressive — and perhaps, in the contest for the nomination, definitive.

Biden won 69 percent of the black vote in Virginia, about 60 percent in Texas and North Carolina, and a staggering 72 percent in Alabama. Those margins helped him build a lead in pledged convention delegates that will be hard for Sanders to erase, especially with populous and delegate-rich Southern states such as Florida and Georgia yet to vote.

There appeared to be some regional and generational differences in which candidates black voters prefer. Biden won the African American vote by considerably smaller margins in California, Massachusetts and Minnesota. Exit polls suggested that, in keeping with his strength among young voters, Sanders likely beat Biden among black voters under 30. But Biden won the overall black vote everywhere. Black America, it would seem, has made up its mind.

Black America is not a monolith. But despite their growing economic, social and cultural diversity, African Americans have remained a strikingly unified voting bloc and make up the most loyal constituency among the Democratic Party’s base. Hispanic voters are more divided: In the 2018 midterms, 29 percent of Hispanic voters backed Republican candidates. Sanders won Hispanic voters on Super Tuesday, especially in heavily Latino states such as Colorado and California. Overall, Sanders won the Latino vote by an average of 9 percentage points.

Among black voters, Biden is clearly helped by having run and served with former president Barack Obama. My guess is that a new Sanders television ad that seeks to make it look as though Sanders and Obama were bosom buddies — when, in fact, they have had sharp ideological differences — will be seen by many black voters as insulting. Anyone who thinks African Americans are low-information voters has never been to a black church, barber shop, hair salon, restaurant or college campus in the weeks before an election. Nobody is going to pull any wool over black voters’ eyes.

“I know Joe. We know Joe. But most importantly, Joe knows us,” Clyburn said in his Feb. 26 endorsement. That was taken as a reference to Biden’s long history as a public servant, his years as Obama’s vice president and his frequent visits to South Carolina. But I took “Joe knows us” as an appeal to the essential pragmatism of African American voters. We are not in the habit of chasing rainbows.

Jesse Jackson won in South Carolina during his 1984 and 1988 presidential runs, but those votes — in what was then a Democratic caucus — were seen as symbolic. No one thought he would actually win the nomination. Mainstream candidates Bill Clinton, Al Gore and John Edwards won the state’s primary in subsequent election years, and in 2008 Hillary Clinton was shown by polls to be cruising to an easy victory — until Obama won the Iowa caucuses. Then everything changed.

When it became clear that Obama could win in an overwhelmingly white state such as Iowa, and thus might actually win a general election, black voters in South Carolina turned on a dime. Clyburn didn’t actually endorse Obama before the 2008 primary but left the distinct impression that he wanted to. Obama won that contest. We know the rest.

Clyburn’s message last week seemed to clarify things for black South Carolina voters, who were trying to figure out how best to defeat President Trump. The landslide those voters gave to Biden seemed to clarify things for black voters in the Super Tuesday states. If Biden is nominated and wins in November, African Americans will have picked a president.

Twitter: @Eugene_Robinson

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