Forecasters split on midterms, but a sweep is possible, maybe likely

By Brett Rowland
The Center Square

Forecasters say Democrats are favored to take the U.S. House this November while Republicans are favored to hold the Senate, yet the likeliest outcome is one party sweeping full control of Congress.

The split reflects two maps pulling in opposite directions: a House landscape tilted toward Democrats and a Senate field that favors Republicans. Yet Decision Desk HQ’s forecast finds that a divided Congress, while possible, is less likely than a clean sweep by either party.

Control of Congress is a means to a fiscal end. The majority sets the agenda on the tax provisions in the 2025 One Big Beautiful Bill Act, on annual appropriations and the recurring threat of a shutdown, and on Social Security’s retirement trust fund, which the 2026 Social Security trustees report projects will run dry in 2032, triggering an automatic benefit cut of about 22% for some 62 million retirees and survivors unless Congress acts.

“The U.S. senators elected this fall will, for the first time, be required to confront Social Security’s insolvency during their term in office,” said Shai Akabas, vice president of economic policy at the Bipartisan Policy Center, who testified at a Senate Finance Committee hearing on the program in June.

Democrats hold the edge in the House. Decision Desk HQ gives them a 62% chance of winning the chamber, and the Cook Political Report finds Democrats end up with a majority in roughly three-quarters of its scenarios, which range from Republicans holding 221 seats to Democrats winning 228.

But the margin looks narrow up close. Sabato’s Crystal Ball rates 213 seats safe, likely, or leaning Republican against 207 for Democrats, with 15 toss-ups left to decide control – a near-even split that underscores how much Republicans’ mid-decade redistricting cushion still matters even in a year favoring Democrats.

Republicans have the Senate advantage. Decision Desk HQ gives them a 59% chance of keeping the chamber. To seize it, Democrats would need to hold all 47 of their seats and flip four Republican ones. Forecasters agree the map runs through a familiar set of states. The Cook Political Report and Sabato’s Crystal Ball both rate Maine and Alaska as toss-ups – though they differ on the rest, with Cook flagging Ohio and Sabato listing Michigan and Iowa. Both give Democrats an edge in North Carolina, where former Gov. Roy Cooper leads.

The forecasts aren’t all measuring the same thing. Decision Desk HQ produces probabilities, the odds a party wins a chamber. Cook and Sabato assign each race a rating, from safe to toss-up, without attaching a percentage. And the generic-ballot average tracks which party voters say they prefer, not how those preferences translate into seats.

That generic ballot is the clearest read on the national mood, and it points to a favorable but not overwhelming year for Democrats. The RealClearPolitics average has Democrats up 4.7 points; Nate Silver’s Silver Bulletin puts the edge at 6.1, down from a 7.1-point peak on June 1. Either way, the advantage trails where Democrats stood at this point in 2018, when the generic ballot sat at 7.6 points. That gap is a large part of why control of Congress remains genuinely uncertain.

Democrats are favored for the House, Republicans for the Senate, yet Decision Desk HQ finds the likeliest outcome isn’t the divided Congress those leanings imply, but a sweep by one party. Four months out, the forecasters just can’t agree on which side will do the sweeping.