Democrats fight for Senate in a double-victory bet

With the US midterms just a day away, all eyes are on potential outcomes. House is already heavily priced for Democrats, so the real question is whether the Senate follows. This is where the market’s still divided.

Per Polymarket, Democrats currently have a 64% chance of sweeping both chambers in the November 3, 2026 midterms, which would bag the party a double victory. This is compared with just 29% for a Republican Senate and Democratic House, and 8% for a Republican sweep.

More than $15.1 million has traded in the Balance of Power: 2026 Midterms market by the time of writing (November 2, 13:00 UTC).

But that 64% headline includes an important detail – the House is pretty much a sure bet at this point. The two outcomes involving a Democratic House, a Democratic sweep at 64% and a Republican Senate/Democratic House at 29% add up to 93%.

This means that the sweep question is basically a Senate question.

Senate is the main battleground

Polymarket's Senate pricing puts Democrats at about 65% to control the chamber, while Republicans are at roughly 36%. That said, Republicans hold a 53-47 majority, so Democrats need four additional seats, while at the same time defending their existing seats. This will not be an easy battle and is a much more competitive proposition than the House.

To make it even more interesting, recent polls and individual campaign developments have put some very red states into play – states that have been traditionally Republican for generations of Americans have opened potential paths for Democrats to get those four seats, while losing none already taken.

And the structure of the market reflects all this. Let's say that Democrats flip the Senate, there's still only a tiny gap between that scenario and a full Democratic sweep because the House is already priced so heavily in their favor.

If we're talking alternatives, the main one would be a divided Congress: Democrats take the House and Republicans retain the Senate.

Volume tells a different story

There is another interesting detail: the outcome with the most trading volume isn't even the one with the highest probability.

The Republican sweep is priced at just 8%. However, it saw about $4.65 million in volume, which is significantly more than any other individual scenario in this market. The Democratic sweep has attracted about $3.81 million, and the Republican Senate/Democratic House outcome has around $2.5 million.

That said, volume measures trading activity, not probability, so this doesn't mean traders overall expect to see a Republican sweep.

However, these several key details show that this market is more complex than just "Democrats are favored."