Thirty five Senate races will be decided on Tuesday, and the outcome will determine whether Republicans keep a majority that is narrow enough to be useful, but not wide enough to be comfortable, or whether Democrats can narrow it further, or even flip it. The Senate map, more than any single race, is the story of this midterm, because it combines national politics with state by state contests that each have their own candidates, issues and turnout patterns.
Republicans hold a 53 to 47 Senate majority, according to reporting on the final weekend, which means Democrats need a net gain of four seats to take control, assuming all seats are counted, while Republicans need to hold their ground to keep it. That arithmetic is why both parties have spent the final weekend on Senate races, even as House races attract more local attention: a single Senate seat can decide whether a president’s nominees are confirmed, whether treaties are ratified, and whether legislation can pass at all.
Senate races differ from House races in scale and in stakes. A senator serves six years, represents an entire state, and votes on confirmations, foreign policy and Supreme Court nominations, as well as on domestic legislation. A Senate campaign therefore attracts national money, national media and national surrogates, including presidents and former presidents, in a way that most House campaigns do not. That national attention can help a candidate, by raising money and turnout, or hurt a candidate, by nationalising a race that voters wanted to decide on state issues.
Why 35 races, not 100
Only 35 of the Senate’s 100 seats are contested this cycle, because senators serve staggered six year terms, with roughly a third up for election every two years. That stagger means the Senate map changes slowly, and that a midterm wave that flips the House may barely move the Senate, if the seats up for election happen to be in states that favour the party in power. Conversely, a modest national swing can flip the Senate, if the seats up happen to be in competitive states.
That is why Senate analysts focus on the map, not just the mood. A national poll that shows one party ahead by a few points does not, by itself, predict the Senate, because the Senate is decided state by state, and a party can win the national vote and still lose the Senate, if its votes are concentrated in states it already wins by large margins, while its opponent wins competitive states by small ones.
What the Senate result will mean
If Republicans keep the Senate, the president will retain a friendly chamber for confirmations and for blocking legislation he opposes, even if the House changes hands. If Democrats narrow the majority, they will gain leverage in negotiations, even without control, because a smaller majority is harder to hold together on controversial votes. If Democrats flip the Senate, a scenario that would require a net gain of four seats, the legislative landscape for the next two years would change fundamentally, with the opposition controlling both chambers, or at least one, and the president facing a Congress that can pass bills he must veto, rather than bills he can sign.
More than 51 million Americans have already voted, a midterm record, and Election Day will add millions more. The Senate map that emerges from that vote, race by race, state by state, will shape confirmations, legislation and foreign policy for the next two years, and it will be decided, as Senate maps always are, not by a single national wave, but by 35 separate contests, each with its own voters, candidates and local story.
