Partisan Intensity in Congress: Evidence from Brett Kavanaugh’s Supreme Court Nomination

Partisan disputes are ubiquitous in Congress. Yet, participation in this bickering varies among legislators. Some eagerly join these fights while others abstain. What explains this variation? Previous research examines this question by studying members’ partisan preferences expressed through votes or bill cosponsorships. However, preference-based studies miss much of the daily congressional bickering and cannot identify which legislators were most involved in the fighting. This paper considers lawmakers’ partisan intensity, the time and effort they devote to partisanship. I argue the same factors that drive other forms of legislative participation—constituent demand, committee service, and a member’s personal characteristics—also predict who joins a partisan dispute. Using Senators’ daily Twitter communications during Brett Kavanaugh’s Supreme Court confirmation, I show legislators’ partisan intensity systematically varied based on these factors. In particular, I find that sexual assault allegations against Kavanaugh altered Senators’ partisan behavior in a predictable manner. This study helps explain why legislators choose to create the partisan acrimony that is omnipresent on Capitol Hill and contributes to our understanding of partisanship, messaging politics, and how social identity affects legislative participation.