Congress is polarized. Fear of being ‘primaried’ is one reason.

In my recent research I examined whether this insurgence of ideological primaries has pushed congressional Democrats and Republicans even further apart.

In at least one way, the answer is yes. Members of Congress who’ve been “primaried” from their party’s ideological extreme are less likely to co-sponsor legislation with someone from the other party. In fact, I find that about one-fourth of the increase in polarization in Congress over the last four decades can be attributed to the increased threat of being “primaried.”

Kurt Schrader (D-Ore.) and primary challengers from the left

Consider, for instance, how Rep. Kurt Schrader (D-Ore.) reacted to being primaried in 2014.

In this May’s Oregon primary, Schrader lost his party’s primary to a more ideologically extreme challenger. But 2022 was not the first time Schrader was challenged from the left.

In 2010 and 2012, Schrader won the Democratic primary unchallenged. After that, Schrader was challenged from the left in every single election year, and fought off two relatively competitive challengers before his loss this year. In 2014, a political newcomer attacked Schrader for working with Republicans to draft legislation that increased the amount of land for timber harvesting. In 2016, Schrader was challenged by a former state House member who aligned himself with Sen. Bernie Sanders (I-Vt.) and said he was running “[b]ecause a lot of Democratic voters want real fundamental change, a political revolution, and they’re not willing to settle for politics as usual.” In 2018, Schrader faced a weak challenge from an inexperienced candidate, again from the left. And in 2020, he faced a more competitive challenge from a candidate who compared himself ideologically to Rep. Alexandria Ocasio-Cortez (D-N.Y.).

Did the recurring primary challenges change Schrader’s behavior in office? According to the Lugar Center, in the 113th Congress (2013-14), which began before his first primary challenge, Schrader was the 10th most bipartisan legislator of the 435-member House of Representatives. But over the next several years, Schrader became less and less likely to co-sponsor bills with Republicans. In the 114th Congress (2015-16), he was the 50th most bipartisan representative; 59th in the 115th Congress (2017-18); and by the 116th (2019-20) and 117th (2021-22) Congresses, he ranked in the high 90s.

Republicans want to hand-count…