Before President Joe Biden exited the presidential race on July 21, pollsters had noticed a consistent trend: Black voters were less solidly in the Democratic camp than in recent elections, including 2020. The Republican Party took notice: During the Republican National Convention, speakers like Rep. John James and Madeline Brame made special efforts to appeal to this key constituency.
Black voters are at least 10 percent of the population in several of the states most likely to decide the 2024 election — from Pennsylvania to Michigan to Florida. They also loom large in Georgia and North Carolina, states that have been close in the recent past. So even small changes in Black Americans' support for Democrats could take key states off the table.
Vice President Kamala Harris's candidacy has the potential to win back Black voters who shifted away from Democrats when Biden was the nominee. But who exactly are these potential new Black swing voters? That's a hard question to answer, in part because polls are rarely optimized to target a demographic that is diverse and larger than the entire population of Canada. By comparing high-quality polls from 2008 to 2024, though, we can see that age has emerged as a major factor in Black voters' support for Democrats — with younger Black voters no longer as solidly in Democrats' camp.
It's unsurprising that the first Black president, Barack Obama, won more than 90 percent of Black voters during his own reelection bid in 2012 and enjoyed strong Black turnout, too. So, to get a baseline of Black voters' support for a white Democrat before former President Donald Trump came on the scene, we've got to look back to the 2008 primaries, when then-Sen. Hillary Clinton was one of the front-runners for the Democratic nomination.
That spring, before the nomination was set, the polling firm Knowledge Networks used population-based methods — surveying respondents online after recruiting them offline — to conduct a panel survey for the National Annenberg Election Survey. With a sample size of 9,888 in its spring 2008 wave alone, this survey had a large sample (962) of Black respondents. Overall, 75 percent of Black adults said they would vote for Clinton in a hypothetical general election matchup with then-Sen. John McCain, who got only 8 percent among Black adults. That's a 67-percentage-point gap.
In early 2024, however, the numbers looked quite different. Political scientist Gall Sigler and I partnered with NORC in February and March of this year to conduct a survey of the 2024 election that included 834 Black adults, and we found Biden led among these respondents by a smaller margin of 61 percent to 20 percent — a gap of only 41 points. (That wasn't far off a March/April YouGov poll of 2,004 Black or African American respondents conducted as part of the National Black Voter Project, which found Biden up 62 percent to 15 percent.) To be sure, that was still a massive pro-Democratic lean. But it was less than Democrats have enjoyed in the recent past.
What changed between 2008 and 2024? A look at Black support by age reveals the answer. As you can see in the chart below, in 2008, Black support for Clinton and McCain was reasonably consistent across age groups. Clinton's support was between 67 and 84 percent among Black Americans across all age categories.
But by 2024, a clear age gap had opened up among Black Americans, at least when thinking about a Biden-Trump matchup. Older Black voters remained overwhelmingly Democratic: For example, Black respondents aged 65-74 supported Biden by 70 points. But as you can see in the next chart, younger Black voters favored Biden by much smaller margins. In fact, Black voters between 25 and 34 gave just about equal support to Biden and Trump.
Of course, it's possible that the key factor wasn't age itself, but rather something correlated with age, like propensity to turn out to vote. Back in April, using the same data set, I found that Trump performed much better — and Biden much worse — among Black voters who turned out less frequently. Biden's margin over Trump was 81 points among Black voters who voted in 2018, 2020 and 2022, while it was only 10 points among those who voted in none of those three elections.
Younger voters tend to turn out less consistently, so maybe Biden's underperformance with young voters was really a weakness with infrequent voters. But vote history wasn't the whole story. When we fit a linear regression model to account for the relationship between prior turnout and voter preference simultaneously, age-based differences in voter preference among Black voters were reduced but not eliminated.
Another factor could have been Black voters' personal experiences with politics. In theory, Black voters who were young adults during the civil-rights era might be especially loyal to the Democratic Party because of the party's role in passing landmark legislation like the 1965 Voting Rights Act when they were most impressionable. But if that were true, we might expect to see a discontinuity for people in their late 70s, since someone who is 77 today was 18 in 1965. Instead, the actual trend by age groups looked more like a straight line, suggesting that other processes were at work.
Indeed, there are other factors that also vary with age and might explain the age gap we saw. Thirty years ago, political scientist Michael Dawson published the book "Behind the Mule," which argued that Black voters are an unusually cohesive voting bloc because of something called "linked fate." To an important extent, Dawson wrote, Black Americans see their own opportunities as tethered to those of the Black community, so they vote overwhelmingly for the party they see as best for that community.
In the early 2024 survey, we measured this idea partly by asking Black respondents, "Do you think what happens generally to Black people in this country will have something to do with what happens in your life, or not?" Overall, our respondents tended to agree, with 75 percent saying what happens generally to Black people has "a lot" or "some" to do with their own life. But there was an age gap here too, albeit a more modest one: Black respondents aged 55-64 reported the highest sense of linked fate (79 percent), while those who were 18-24 reported the lowest (60 percent). It's plausible, then, that weaker perceptions of linked fate among younger Black voters helps explain the age gap in presidential support.
But let's be precise about the magnitude of the relationship. As respondents shifted from the lowest sense of linked fate ("not at all") to the highest ("a lot"), their support for Biden increased by about 0.11 on a 0-1 scale, according to a linear regression model. So linked fate was a part of the explanation, but it was not the whole story either. Even when we accounted for linked fate in statistical models, the age gap remained meaningful.*
For years, Democratic campaigns have devoted a lot of time and energy specifically to mobilizing Black voters. That will surely also be the case this year since, even if the Biden-level performance holds, Democrats will still benefit from high Black turnout — but some quick math shows us that those benefits may be dampened compared to prior years.
If Black voters as a whole cast more than 90 percent of their ballots for the Democrats, turning out 100 new Black voters will result in a net gain of 80 Democratic votes — that's assuming, though, a very high margin of Democratic victory among Black voters, and that the Black voters who only vote occasionally have the same levels of support as those who vote consistently. But if Black voters who wouldn't have otherwise voted are only with the Democrats by a margin of, say, 47 percent to 29 percent, turning out 100 new Black voters produces just 18 votes for Democrats on average. So if Democrats are losing the support of younger Black voters or less engaged Black voters, they may find that their get-out-the-vote efforts don't bear the same fruit as in past years.
Sophia Leung and Gall Sigler contributed research.
*In these regression models, we also saw that women were about 0.07 points (on the same 0-1 scale) more pro-Biden and that neither income nor education was a strong predictor of Black respondents' presidential preference.