On January 30, readers of The New York Times' website might have noticed something intriguing in its "City Room" section. Nestled between outtakes from a night with young Republicans in Staten Island and part four of a five-part series on tenant-landlord issues was the headline: "On Michelle Obama's Guest List: Alma Rangel. What followed was a report on how the wife of House Ways and Means Committee Chairman Charlie Rangel, the legendary Harlem representative, had dropped by an Obama fund-raiser on the Upper East Side.

What made the item so curious is that Rangel is a longtime Hillary Clinton supporter. He's credited with the inspiration for her maiden Senate bid in 2000; the next year, he played a pivotal role in bringing Bill Clinton's post- presidential office to 125th Street, Rangel's backyard. That such an inner member of Rangel's inner circle would be caught nibbling bruschetta behind enemy lines seemed like a major breach of protocol.

Or was it? A few days later, Alma Rangel came out from the shadows and officially endorsed Obama. Atmospherics being what they are in politics, it's hard to believe she would have taken that step without at least a tacit green light from her husband. Less hard to believe is that Rangel would have given it. With African Americans now overwhelmingly embracing Barack Obama--something that remained in doubt as recently as two months ago--these can be lonely times for the black elected officials who've endorsed his chief rival.

It was, of course, the night of the South Carolina primary when it first became obvious that African American voters had parted company with many black leaders on the matter of presidential preferences. As the exit polls gushed in showing Obama winning roughly 80 percent of the black vote, Hillary endorsers like Sheila Jackson Lee, an African American representative from Texas, suddenly found themselves waging a rearguard p.r. battle. "In South Carolina, you saw a convergence of pride and respect on the outstanding candidates that they had, and certainly in Senator Obama," was all the grim-faced Jackson Lee could muster. "There's nothing wrong with that. People choose who they want to choose."

In retrospect, the South Carolina results exposed a divide in the way the campaigns courted African American pols. The Clintons had largely operated from a top-down model--relying on personal relationships and the self-interest of black politicians and hoping their constituents would follow suit. In one now- famous episode, they went so far as to give State Senator Darrell Jackson, a prominent pastor, a consulting contract. By contrast, the Obama campaign generally observed a "no walking-around money" policy. It made the case to African American politicians by pointing to its grassroots strength (though it didn't hurt that Obama's PAC handed out nearly $200,000 to candidates and political groups in early primary states last year). "After we won Iowa, I went to a lot of leaders and said, 'You better get on the train before it comes rolling through here,'" recalls Anton Gunn, Obama's South Carolina political director. "Some laughed it off; others recognized this was for real."

Often the divide was generational. With some notable exceptions, the profile of the typical African American Clinton endorser was someone who'd supported Bill Clinton and had enjoyed some amount of White House largesse in return. (As president, Clinton had headlined multiple fund-raisers for Jackson Lee, for example.) For his part, Obama tended to clean up among those who had entered elective office during the post-Clinton era. Freshman Georgia Representative Hank Johnson told me he got a call from Obama before he was even sworn in last January. He was spoken for by the time a Clinton operative sidled up to him in the spring.

Whatever the nature of the split, it wasn't hard to see the problem for the Clinton supporters in the aftermath of South Carolina. "For individuals who endorsed Senator Clinton, [the risk was always that] Obama would prove to be enormously popular in the black community; he'd win the lion's share of your district," says Alabama Representative Artur Davis, who endorsed Obama last February. "You'd find yourself at odds with your constituents, and an opponent could use that against you.

It's still hard to imagine that people like Rangel--icons who've been reelected with little or no opposition in their districts for decades--will face much of a challenge. (Hillary actually carried Rangel's district Tuesday night, thanks in part to the large Hispanic vote there.) For others, the problems may just be beginning. According to Jamal Simmons, a political consultant who works in heavily African American areas, the effect the Obama campaign is having on black communities could be similar to the effect the Dean campaign had in upscale liberal enclaves in 2004: In many of these places, turnout has suddenly doubled, giving a local representative tens of thousands of new voting constituents to worry about--many of whom cast their first votes for Barack Obama.

The new, Obama-supporting demographic is much younger and more male than the existing black electorate, says Obama pollster Cornell Belcher. They're unlikely to respond well when cautioned against "leapfrogging"--a term the machine pols use to stress the importance of paying one's dues (and which Hillary invoked during a recent appearance with Rangel). And they could easily form a base for future campaigns across the country.

There is historical precedent for such mobilization in the black community. After Jesse Jackson ran for president in 1984 and '88, many of the activists and voters he attracted stuck around to help elect a generation of black politicians--most prominent among them David Dinkins, who won his race for mayor of New York in 1989. "If not for Jesse Jackson and the kind of electoral coalition he was able to put together, Dinkins would not have been possible," says Wellesley political scientist Wilbur Rich, an expert on urban politics. "Dinkins had no base outside of Manhattan."

And Obama isn't just bringing new voters into the process. He's bringing new donors, too. As Simmons puts it: "You've got a group of lawyers or business people who just finished raising $300,000 for Barack Obama. They're saying to themselves, 'It costs a million to run for Congress. ... We're a third of the way there.'" This is never the kind of calculation an incumbent wants to encourage.

A savvy politician will stay abreast of these developments and pivot to accommodate them. "I do have a network of people that are not limited to my district that I communicate with all the time," says South Carolina's Jim Clyburn, the House's third-ranking Democrat. A week out from primary day, Clyburn was detecting all manner of frustration with the Clintons' polarizing tactics. Only a longstanding promise to the state party, and the urging of his wife and daughter, kept him on the sidelines. But, once the votes were counted, he immediately turned his attention to his new pro-Obama constituency. "Sunday afternoon, I went into the Democratic Party headquarters," he says. "They showed me how many people voted in the sixth congressional district. I got a printout. Every one of those people will hear from me in one way or another between now and the election."

Those of Clyburn's colleagues who endorsed Hillary should plan on doing the same. Greg Moore is the executive director of the NAACP Voter Fund and a friend of Cleveland Representative Stephanie Tubbs Jones, another Clinton supporter. He attributes Tubbs Jones's endorsement to her work with Hillary on an election- reform bill after the problems in Ohio in 2004, and he admires her loyalty. But he suspects there will be fallout. "Her district is fifty-five percent African American," Moore told me. "People say, 'Why isn't she supporting Barack Obama?' It does make her life less pleasant than it would be if she were endorsing an African American." The post-South Carolina anti-Clinton backlash did little to help her situation.

Tubbs Jones will probably weather the rough patch. "I haven't felt any unpleasantness; that's not to say I may not in the future," she says, stressing that her relationship with the Clintons goes back years and that she felt Hillary was the most qualified candidate. But, according to an Atlanta-based political strategist who works in the African American community, Representative David Scott could face more serious problems in Georgia, where Obama won nearly 90 percent of the black vote. "There are definitely rumblings among young people," says the strategist. "[The Hillary endorsement] was a lot riskier for Congressman Scott." Complicating the situation is the fact that there are now at least three formidable African American politicians raising money for what's expected to be an intensely competitive Atlanta mayor's race in 2009. At least two of those candidates will lose, leaving them with an organization, a fund-raising network, and an itch for higher office. It wouldn't be shocking if one of them challenged Scott.

Meanwhile, in Detroit last month, Clinton lost overwhelmingly to "uncommitted"--the box many local pro-Obama groups had encouraged their members to check because Obama himself was not contesting Michigan. When I asked Judiciary Committee Chairman John Conyers, a long-serving Detroit representative, whether he would have been in trouble had he endorsed Clinton rather than Obama, he told me, "I think it would have created tension. I don't think it would have been a serious problem ... but it only takes one person to announce in your district that they're running against you." That may be one reason why Carolyn Cheeks Kilpatrick, another Detroit-area representative, kept her presumed support for Hillary quiet in the weeks leading up to the primary. (Kilpatrick never endorsed but took heat from her colleagues in the Congressional Black Caucus last September after featuring Hillary at a town hall-style forum during the CBC's annual conference.)

Still, one of the things you hear most often from Obama endorsers like Conyers has less to do with avoiding a challenger than avoiding social embarrassment in the years to come. "To me, there's a historical consideration in this as well," Conyers says. "How in the world could I explain to people I fought for civil rights and equality, then we come to the point where an African American of unquestioned capability has a chance to become president and I said, 'No, I have dear old friends I've always supported, who I've always liked.' What do you tell your kids?" Charlie and Alma Rangel may have wondered the same thing.

Noam Scheiber is a senior editor at The New Republic.