Polymarket
KalshiIllinois Senate 2026: Durbin's Open Seat Is Priced as if He Were Still on the Ballot
The Illinois Senate odds 2026 market treats an open seat as if it were not open: Dick Durbin is leaving the Class II seat, and the market rests on the view that the seat's voters, not its occupant, decide the result. Juliana Stratton, the Democratic nominee, faces Don Tracy, the Republican nominee, on November 3, 2026, and the State Board of Elections' results show Democrats winning both of Illinois's Senate seats by wide margins in 2020 and 2022. The live board above carries Kalshi's and Polymarket's current prices.
Why the Illinois Senate Seat Is Open
Durbin holds the seat now. The Senate's own list of members names Richard J. Durbin, a Democrat, as the Class II senator from Illinois, and Wikidata records his current term as beginning January 3, 2025. He is not on the State Board of Elections' list of general-election candidates. Fox News reported on March 17, 2026 that he announced he would not seek re-election, ending a Senate career that began with his election in 1996. Tammy Duckworth, also a Democrat, holds the Class III seat, which is not on this year's ballot.
The State Board of Elections' list, as of October 16, 2026, has three candidates for U.S. Senator: Juliana Stratton for the Democrats, Don Tracy for the Republicans and Whitfield Harrington Jr for the American Center Party. An independent filing was removed from the list on July 14, 2026.
Who Stratton and Tracy Are
Stratton is the sitting Lieutenant Governor. Wikidata records her in that office since January 14, 2019, and the office's own website names her. Because she is running for the Senate, she is not on the governor's ticket this year; Christian Mitchell is.
She won a contested Democratic primary on March 17, 2026 with 507,689 votes, 40.39% of the party's total, against two members of the U.S. House. Raja Krishnamoorthi, who represents the 8th District, took 411,150 votes, 32.71%, and Robin Kelly, who represents the 2nd District, took 229,788, 18.28%. Fox News reported that Governor JB Pritzker put his political weight behind Stratton in that primary. The result also opened two House seats, which is why the 8th and 2nd Districts have new nominees this fall.
Tracy won a six-way Republican primary on March 17, 2026 with 215,523 votes, 39.96%, ahead of Jeannie Evans with 122,840, 22.78%, and four others, which made him a plurality nominee as well. Fox News describes him as a former chair of the Illinois Republican Party who ran on lowering living costs through competition, consumer choice and negotiated prescription drug prices.
The primary turnout gap is worth noting once. Stratton's vote alone, 507,689, was more than twice Tracy's, and the Democratic primary drew well over twice as many voters as the Republican one. Primary turnout is not a general-election forecast, but it shows where each party's most engaged voters were in March.
Why the Illinois Senate Price Barely Registers an Open Seat
What the price is saying is that the seat belongs to the electorate rather than to Durbin. The record behind that read is long and consistent. In 2020, the last time this seat was on the ballot, Durbin won with 3,278,930 votes to 2,319,870 for Republican Mark C. Curran Jr., a margin of almost a million votes, with Willie L. Wilson taking 237,699 as a third-party candidate. In 2022, for the other seat, Duckworth beat Kathy Salvi by 2,329,136 votes to 1,701,055. In the 2024 presidential race, the Clerk of the House's statistics show Illinois's Democratic electors with 3,062,863 votes to the Republican slate's 2,449,079.
On October 16, 2026, Polymarket had the Democratic contract at 98%, the cheapest Yes on that side, against Kalshi's 99.5%, and Polymarket's 2% was the cheapest Republican Yes, against Kalshi's 3%. That means the venues treat a Stratton loss as close to unthinkable, which is a stronger statement than any single poll of an open-seat race could make on its own. The price is built on the state's voting history, not on the candidates. The board carried about $36K in lifetime volume on Polymarket and about 19,000 contracts on Kalshi as of October 16, 2026, split nearly evenly between the two contracts on both venues, so the Republican side has drawn about as much trading as the favorite even at a very low price.
The governor's race on the same ballot points the same way. The venues price Pritzker's re-election with similar confidence, and Stratton has been his Lieutenant Governor since January 2019. A voter who returns Pritzker and splits the ticket for the Senate would have to do so in large numbers for the price to be wrong.
The Case Against the Illinois Senate Read
The strongest case against the read is that an open seat removes an advantage both of the last two Illinois Senate winners had, incumbency, and the market prices it as if nothing changed. Stratton has never held the seat, while Durbin had held it since winning it in 1996, as Fox News reported. A Republican who reads the 2020 result as Durbin's personal margin, rather than the party's, sees more room than the Republican price allows.
There is also the primary itself. Stratton won with about four in ten Democratic primary votes after a three-way fight, and Krishnamoorthi's 411,150 votes show a large bloc of Democratic primary voters chose someone else. A reader who holds the counterread would say a nominee who won a plurality has more to prove in November than the price suggests.
The answer the price gives is that the 2020 and 2022 results were not close, and that a crowded primary for an open seat says more about the size of the opportunity than about the nominee's weakness. The counterread needs a shift of hundreds of thousands of votes from 2020 and 2022, and a poll showing that shift would be the first evidence for it.
What Changes the Illinois Senate Read
The read would be wrong if independent evidence shows the open seat behaving differently from the state's past Senate races. The dated tests:
• Public polling: Any independent survey of the Stratton and Tracy race before November 3, 2026. A single-digit race would be the first evidence the price has run ahead of the voters.
• Third-party share: Whitfield Harrington Jr of the American Center Party is on the ballot; Willie L. Wilson's 237,699 votes in 2020 show what a third candidate can draw from the two parties.
• The voting calendar: Online registration closes October 18, 2026, early voting at permanent sites opens October 19 and mail-ballot applications sent by mail are due October 29.
• The count: Polls are open 6 a.m. to 7 p.m. on November 3. Mail ballots postmarked by Election Day and received within 14 days are tabulated through November 17, and the State Board of Elections proclaims the results by December 4, 2026.
When the Illinois Senate Market Resolves
Kalshi resolves its Democratic contract Yes if a representative of the Democratic Party is sworn in as a senator from Illinois for the term beginning in 2027, and its Republican contract on the same test; it lists an expected settlement of January 4, 2027 and allows accelerated determination once a consensus of media organizations projects the winner. Polymarket resolves on the winner of the 2026 Illinois U.S. Senate election, inclusive of any run-off, once the Associated Press, Fox News and NBC all call it for the same candidate, and on the official certification otherwise. A candidate represents a party on Polymarket by being its nominee, so a Harrington win would pay neither party's contract.
Related Illinois Markets
Stratton's old ticket mate is on the Illinois governor odds page, which prices the Pritzker and Bailey rematch. The two House seats her primary opponents gave up have their own boards: the Illinois 8th District odds and the Illinois 2nd District odds. The other closely priced districts are the Illinois 17th District odds, the Illinois 11th District odds and the Illinois 4th District odds. The Illinois elections page lists every race on the ballot.
