For the first time in this race’s history, prediction markets are favoring Democrats to win the Senate.
Contracts on both Kalshi and Polymarket flipped to show Democrats with a roughly 51% chance of winning Senate control, against 49% for Republicans. Kalshi spokesperson Jack Such called it a genuine milestone. “The Democratic Party is now favored to win the Senate for the first time in the race’s history,” he told Decrypt. “The race is now essentially a coin flip, with Democrats having a 51% chance to win.”
Such also pointed to what’s actually been driving the shift.
“Since the start of American military involvement in Iran roughly 16 days ago, the Democrats’ implied probability of controlling the Senate has increased by about 11 percentage points,” he said. That’s a striking swing for two and a half weeks, and it lines up with a market that had Republicans as high as 60% favorites to hold the chamber back in early July.
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Polymarket’s own “Balance of Power” market tells a similar story from a different angle.
A full Democratic sweep of both chambers now sits at 51%, ahead of a split Congress with Republicans holding the Senate at 36%, and a complete Republican sweep trailing at just 12%, across $11 million in trading volume. The platform’s own market summary lays out why: “Democrats hold a consistent 6-point edge on the generic congressional ballot amid a national environment marked by sub-40% presidential approval and widespread dissatisfaction with the direction of the country.”
BREAKING: Democrats are now projected to sweep the 2026 midterms, taking both the Senate & House.
51% chance. pic.twitter.com/BLi4Z7lH3d
— Polymarket (@Polymarket) August 31, 2026
CNN polling analyst Harry Enten has been tracking this shift for months.
Back in March, with Kalshi’s Senate odds for Democrats sitting at just 46%, up from 28% in January, he described the trend as still building. “The whispers are getting louder,” he said on air. By mid-August, on The Source with Kaitlan Collins, his tone had changed considerably. Asked what the numbers meant for Trump’s political operation, he didn’t hedge. “I’m running scared. I’m running scared,” he said. “You know, look, the numbers don’t lie. I tell it like it is. Whatever the numbers say, that’s where I go.”
That same week, breaking down a set of Southern battlegrounds, Enten highlighted a shift with no recent precedent. “So three Southern states, three former Confederate states, and you see that Democrats are leading in them all,” he said on CNN. “There has not been a Senate Democratic win in North Carolina since 2008.”
The map still stands in the way of calling this settled.
Republicans hold a 53-47 Senate majority and are defending 22 of the 35 seats up this cycle, including special elections already underway in Ohio and Florida, while Democrats need a net gain of four seats to flip control.
According to DeFi Rate’s mid-August analysis, Democrats need to “defend Georgia and Michigan, flip North Carolina and Maine, then win two of Ohio, Texas and Alaska, or get help from Iowa or Nebraska.” That’s a demanding sequence, but Kalshi’s own county-level tracking shows Iowa and Texas have already shifted from “Lean Republican” to “Toss-up” as of August 20, with Kansas moving the opposite direction toward Republicans the same week.
Featured image via X screengrab
