In 2025, when the Senate convened, Republicans held a majority of seats. It would have taken six seats changing hands to flip that majority. A flip in the House would have taken only three. In 1869, it would have taken 25 Senate seats and 44 House seats to do the same.
Congress used to swing between wide and slim margins. Not anymore. Since 1995, neither party has held more than 59% of either chamber at the beginning of Congress every other January. Margins are so thin that a handful of seats, not dozens, now decides who’s in charge.
