With the 2026 midterms approaching on Nov. 3, the decade has yet to produce the kind of election-night upheaval that has periodically redrawn Washington’s political map. The last opportunity for a major shift this decade is now at hand, with forecasts pointing to a possible Democratic takeover of the House and perhaps the Senate as well. The 2022 election fell short of the widely expected Republican “red wave.” Democrats held the Senate, while Republicans won the House by a narrow margin, ending Nancy Pelosi’s second run as speaker. Republicans then spent much of the following two years struggling to unite behind a speaker of their own. Midterms typically draw lower participation than presidential elections: overall vote totals fall by about one-third, as voters less likely to turn out without a presidential race on the ballot stay home. Yet those who do vote decide every House seat, one-third of the Senate and a large share of state legislative and gubernatorial contests. The stakes reach well beyond Capitol Hill, shaping state policies and the political talent that may rise to national office. The past century offers a series of sharp midterm reversals. In 1930, amid the economic collapse that became the Great Depression, Republicans lost 52 House seats and eight Senate seats. Democrats gained control of the House after early-1931 special elections and went on to dominate Congress for much of the following period. Republicans swept back into control of both chambers in 1946, as President Harry Truman faced widespread dissatisfaction after World War II. In 1958, President Dwight Eisenhower’s party suffered another major setback, leaving Republicans with just 35 Senate seats. The large Democratic Senate majority that followed helped provide the votes for landmark civil-rights legislation in the 1960s. Later elections brought their own consequences. Democrats lost 47 House seats in 1966 as President Lyndon Johnson’s standing was strained by the Vietnam War. The 1974 midterms, held months after Richard Nixon resigned amid Watergate, cost Republicans 48 House seats. In 1986, Democrats gained eight Senate seats, giving them a 55-45 majority and the power to block or challenge parts of President Ronald Reagan’s agenda. The 1994 election brought Republicans a 54-seat net gain in the House and eight seats in the Senate, restoring GOP control of both chambers for the first time in decades. Republicans also took the House in 2010 amid a weak economy and public opposition to the Affordable Care Act. In 2006, dissatisfaction with the Iraq War helped Democrats win both chambers, and Pelosi became the first woman to serve as House speaker. The pattern is not automatic. Republicans gained seats in President George W. Bush’s first midterm in 2002, shortly after the Sept. 11 attacks. Nor does a midterm result alone dictate the next presidential election. But elections held between presidential contests can serve as a blunt public verdict on the party in power, particularly when voters are worried about the economy or believe the governing party has lost momentum. The 2026 contest combines economic concerns, including energy prices, with negative perceptions of incumbents, factors that have featured in previous midterm swings. If Democrats win control of either chamber, the result could reshape the remainder of the president’s term and set the direction for state and national campaigns to come. If the election produces only narrow changes, the decade may close without a midterm on the scale of the historic reversals that preceded it.