Republican majorities in both chambers of the 119th Congress, combined with longstanding party discipline under President Trump, have kept the threshold for a two-thirds override vote out of reach on contested legislation. Historical patterns show successful overrides occur in only about 4 percent of cases, and recent attempts—such as January 2026 House votes on pipeline and land bills—fell short despite initial bipartisan passage margins. Traders assign a 95.1 percent implied probability to no override occurring because narrow GOP margins and White House leverage make sustained cross-aisle coalitions unlikely on most measures. Late-session developments, including war-powers disputes or appropriations fights where support holds above two-thirds after a veto message, remain the primary scenarios that could still shift the outcome before year-end adjournment.