Modeling the Changing Patterns of Policymaking

A new study by Caltech political scientist Alexander Hirsch and Stanford’s Ken Shotts uses mathematical models to assess how the Senate’s filibuster influences policy development. The research examines how ideological disagreement among legislators affects the effort invested in crafting high-quality proposals and the likelihood of their passage. The filibuster requires a supermajority of 60 senators to end debate and advance a bill, a threshold that can delay or block legislation entirely.

The models reveal that in moderately polarized legislatures, the filibuster can inadvertently benefit centrist senators by encouraging highly invested lawmakers to produce detailed, high-quality proposals. However, in highly polarized settings, the filibuster exacerbates gridlock by stalling nearly all policy efforts, undermining the legislative process. Hirsch and Shotts compare the modeling approach to constructing hypothetical political environments to test how institutional rules shape outcomes.

The filibuster originated in the 1800s as a tactic to delay votes by extended debate, later formalized in 1917 with a two-thirds majority rule to end debate. By 1975, the Senate reduced the threshold to a three-fifths supermajority, or 60 votes, to invoke cloture. The rule’s persistence suggests it serves a stabilizing function despite its reputation for slowing progress, according to the researchers.

Hirsch emphasizes that calls to eliminate the filibuster without understanding its systemic effects risk unintended consequences. The study’s framework can be applied to broader questions about institutional design, highlighting the need for careful analysis before altering long-standing legislative procedures. The research underscores the complexity of policymaking and the trade-offs inherent in institutional rules.