One Week Out, Kalshi Traders Hand Democrats 63% Shot at Congress Sweep

The 2026 midterms land a week from Tuesday, and the betting crowd has already made up its mind. Traders on Kalshi put a 63% chance on Democrats winning control of both the House and Senate, according to CNBC. That's a two-to-one edge over the field, and the number has barely budged since the start of October.

The rest of the board tells the same story. Republicans sweeping both chambers sit at just under 10%, while a split verdict — Democrats take the House, the GOP holds the Senate — carries a 29% chance. Kalshi resolves its contracts using official data from the U.S. Congress, so there's no gray area once the votes are counted. Over on Polymarket, Democrats get slightly better treatment: 65% to sweep both houses.

Democrats haven't always looked this comfortable. Before early September they were under 50% to take both chambers, and earlier in the year their odds sat around 30% — before the U.S.-Iran war and higher gas prices started pinching consumers. Then the numbers flipped, and they've stayed flipped.

If you're wondering how much weight to give this, the platforms have a defense ready. They argue that traders' odds tend to play out at roughly that rate — a candidate priced at 20% pulls the upset about 20% of the time. The caveat cuts both ways, though: prediction markets don't use traditional polling methodology and aren't a substitute for polls. They've also misfired. On Sunday, markets gave high odds to right-wing candidate Flavio Bolsonaro in Brazil's presidential election before polls closed, and incumbent left-wing president Lula da Silva won anyway. Some Democratic primary markets this cycle drew similar criticism after handing sky-high odds to candidates who barely won or outright lost.

Traditional polling still broadly favors Democrats in the national popular vote for the House and shows them competitive in a string of red-state Senate races that will settle the upper chamber. House Speaker Mike Johnson, R-La., isn't having it. Appearing on Fox News Monday, he dismissed the surveys outright. 'We've been from coast to coast,' he said, 'and I'm telling you, the polling is inaccurate.'

Worth noting for transparency: CNBC and Kalshi have a commercial relationship that includes customer acquisition and a minority investment. Either way, the clock is running. Seven days, two chambers, and a market that thinks it already knows.