Joe Biden Just Killed the Momentum Theory of Politics

Politicians desperately want it. Journalists brag about seeing it. And some scientists claim it doesn’t even exist. It’s momentum—the idea that strong polls and early primary victories propel candidates to even more strong polls and even more primary victories.

The specter of this mythical political force haunts TV coverage of the primary season. Past research has indicated that the word momentum is uttered 60 times a day on broadcast and cable news. But try applying the concept to the 2020 Democratic primary:

• Pete Buttigieg won Iowa and nearly won New Hampshire. Journalists at Politico, the Boston Herald, and CNN exclaimed that he was gaining momentum. Then he got crushed in Nevada and South Carolina. On Sunday night he suspended his campaign.
• Amy Klobuchar’s third-place finish in New Hampshire minted a crop of cursed portmanteaus: Klomentum, Klobesurge, Klobucharge. But in the real world of real words, no momentum, surge, or charge materialized. She finished sixth in the next two states and dropped out on Monday.
• Bernie Sanders followed up his mildly underwhelming performance in Iowa with a razor-thin win in New Hampshire. Then he trounced the field in Nevada, establishing himself as the hands-down favorite to win the nomination. A week later, Joe Biden crushed him by almost 30 points in South Carolina.
• As for Biden, his primary season has been a roller coaster. He came in fourth in Iowa and fifth in New Hampshire. Both losses were devastating enough that coverage of his campaign took on a premortem vibe and pundits confidently predicted he didn’t have a shot (unlike, say, Buttigieg). But his win in South Carolina was so convincing, it not only reestablished him as the co-front-runner but also got two of his moderate rivals to drop out.

If anything, momentum in this primary has punished its possessors as often as it’s rewarded them. Just look at Elizabeth Warren, who raced to the front-runner spot in October and November before immediately plunging in the polls. Warren’s experience suggests that having momentum is often like having the ball in the NBA. Yes, the ball exists, and yes, it’s nice to have it, on account of the whole point of the game is to score. But as any casual fan of basketball knows, the player with the ball receives particularly rough treatment from the opposition. They are swarmed by defenders, scrutinized by announcers and casual fans, and criticized if they make a mistake. Momentum is a sign of success that sends a bat signal to rivals: Come at me. And rivals often do.

This primary season has wrecked the idea that momentum lasts more than a few milliseconds, and given life to another grand theory of politics: Demographics are destiny.

Buttigieg and Klobuchar, whose appeal had always skewed to white voters, exceeded their national polling averages in the very white states of Iowa and New Hampshire. Sanders, who has a high floor of support among young people, low-income voters, and Latinos, cleaned up in Nevada, which is almost one-third Latino. And Biden, whose support is highest among black voters and the elderly, dominated in South Carolina, which has the country’s fifth-highest share of black voters.

The demographic-destiny theory has some grounding in political science. A 2019 paper on the “momentum myth” from researchers at Vanderbilt University found that the characteristics of each state’s electorate, rather than some national force of momentum, explained the state-by-state outcome of the 2016 Democratic primary. Across the country, Sanders won where voters were whiter and younger, and Hillary Clinton won in states that were older, with larger black populations.

The Vanderbilt paper found that primary victories don’t change many minds, but they do open donor wallets. And more money means more chances to pick up delegates. Nate Silver, who has criticized reporters for obsessing over polling momentum, has still built an election-forecasting model that rewards candidates after early caucus and primary wins because, as he’s written, early state wins typically lead to more donations and a higher likelihood that rivals will drop out.

If the Democratic nomination process comes down to Joe Biden versus Bernie Sanders, it will be a showdown between the only two candidates who built a steady and sizable base: Sanders with young voters (especially Latinos), and Biden with old voters (especially African Americans). This is an age when the parties are broken, primary voting is fractured among many viable candidates, and the party establishment is too weak to clear the lane early for its preferred nominee. These sorts of contests aren’t chiefly about momentum, or early acceleration. They’re about building a base that’s real, resilient, and ready to vote.