How Game Theory Explains Joe Manchin’s Defense of the Filibuster

In January 2022, Senate Democrats, with a nod from President Joe Biden, attempted to change the chamber’s filibuster rules so they could pass voting rights legislation. Predictably, Republicans objected. But the procedural move was also opposed by Sen. Joe Manchin, a longtime defender of the filibuster, the rule that allows the minority party to block bills that can’t get a 60-vote supermajority.

The West Virginia Democrat reiterated his support for preserving the supermajority threshold, saying that it “plays an important role in protecting our democracy from the transitory passions of the majority and respecting the input of the minority.” The filibuster stayed in place and the voting rights bill stalled.

Manchin’s stance has perplexed and angered his fellow Democrats. Why, they wonder, does he oppose simple-majority voting, which would enable their party to pass key legislation — and presumably boost his power as the swing vote in a nearly evenly divided Senate?

The answer, explains Keith Krehbiel, a professor emeritus of political economy at Stanford Graduate School of Business, is embedded in a phenomenon he calls the Manchin Paradox. “The paradox is that, although Joe Manchin is the pivotal voter in the U.S. Senate under simple-majority rule, he does not want to decide by simple-majority rule. That’s counterintuitive.”

In a new paper, Krehbiel analyzes this “enigma” by drawing on game theory and his work as the originator of the pivotal politics model. He and coauthor Sara Krehbiel, an associate professor of mathematics and computer science at Santa Clara University (and his daughter), find that Manchin’s posture not only is logical but also “reveals a deep, pervasive, and nonobvious force in democratic politics”: the appeal of seemingly anti-majoritarian procedures such as the filibuster.

Manchin in the Middle

Manchin occupied a unique position in the session of Congress that opened in 2021. Senate Democrats held the slimmest of majorities due to Vice President Kamala Harris’s tie-breaking vote. On many issues, Manchin was squarely in the middle, making his vote essential to getting anything passed with a 51-vote majority.

This made him what political scientists call the pivotal or — in the case of simple-majority voting — median voter. “The median voter will be able to bargain with Senate leaders on both the right and the left to bring policies exactly to his ideal point,” Krehbiel says. “Then, at his ideal point, the proposal will get half the votes plus one, and they can all go home.”

This isn’t unique — one senator is always the median voter. (Sen. Kyrsten Sinema of Arizona also assumes the role at times in the current Congress.) Yet Manchin has received more attention than other senatorial swing voters due to the polarized nature of Congress and his tendency to be a holdout on Democratic bills such as the Inflation Reduction Act (which, as a reconciliation bill, wasn’t subject to the filibuster).

However, just how much benefit Manchin can extract by standing his ground depends on the rules that govern the Senate. Krehbiel illustrates this by describing a hypothetical appropriations bill. Suppose that Senate Majority Leader Chuck Schumer would like to spend $10 billion. Under simple-majority rules, Schumer only has to win his fellow Democrats’ votes, including that of the pivotal voter: “Median Joe” Manchin.

Imagine that Manchin wants to spend $4 billion and becomes less happy as proposals deviate from his ideal amount. If Schumer proposes a figure just shy of $8 billion, Manchin will vote yes because he just barely prefers that amount over no spending at all. Yet what does he get from being the pivot? Not much: As Krehbiel and Krehbiel write, “[F]rom a payoff perspective, it is as if the pivotal voter never even played the game.”

Now, consider the same scenario with the filibuster in place. Schumer must pick up several Republican votes to pass the bill, so the swing voter is now a moderate Republican, such as Utah Sen. Mitt Romney or Alaska Sen. Lisa Murkowski. “Because they’re pivotal under supermajority rule, Chuck Schumer has to concede more, making a still more moderate proposal around $6 billion, which is closer to Manchin’s $4 billion ideal,” Krehbiel says. This makes Manchin better off, even though he is no longer the pivot. “He does better under the supermajority voting than simple-majority voting.”

The Silent Majority?

This explanation of why Manchin prefers the filibuster contradicts many politicians’ and pundits’ take on what makes him tick. They incorrectly assume that his opposition to simple-majority voting is self-defeating since it sacrifices his power to cast the deciding vote. And even his stated reasons for retaining the filibuster, such as his commitment to bipartisanship, overlook a simpler reality: The 60-vote threshold gets Manchin more favorable outcomes than simple-majority voting.

The Manchin Paradox doesn’t just describe Joe Manchin’s behavior. It also helps explain the Senate’s insistence on following procedural traditions that appear to disadvantage the majority party. Proposals to do away with the filibuster, such as the so-called nuclear option, have become routine at the start of each session of Congress. Doesn’t this suggest a genuine desire for majoritarian reform? “I would suggest that such a ‘genuine desire’ is disingenuous,” Krehbiel says. He notes that calls for scrapping the filibuster invariably come from the majority party, whether it’s the Democrats or Republicans. “Parties are egregiously inconsistent in their supermajoritarian antipathies and proclivities,” he says.

The filibuster’s critics contend that it’s archaic and antidemocratic, and causes gridlock. Yet Krehbiel notes that these procedures have also produced durable legislation that’s closer, on the whole, to what the median voter in the Senate wants. “Gridlock and filibusters tend overwhelmingly to get bum raps,” he says. “But if you’re a moderate who values policy stability, gridlock is a feature of American government — not a bug.”