Two days before Election Day, the runner-up in Michigan’s Democratic Senate primary endorsed the Republican. Rep. Haley Stevens, D-Mich., appeared with former Rep. Mike Rogers, the Republican nominee, at Perfecting Church in Detroit on Sunday morning, then posted a video endorsing him. Within hours, Democrat Abdul El-Sayed’s price on the prediction markets had dropped from the high 70s to 69 cents.
The question for traders: Is that move a fair price for a real shock, or is it a discount on the favorite?
How Michigan Senate odds moved
The race has drawn about $51.1 million in trading on Kalshi and Polymarket, making it one of the most heavily traded Senate contests on the board. The drop wiped out El-Sayed’s late-October rally. He hit 76 cents, an all-time high on Kalshi, on Oct. 30, and he gained 2 cents Saturday even as his feud with Stevens went public.
What happened
Stevens narrowly lost the August primary to El-Sayed and endorsed him afterward. Then the relationship broke down over Israel. Last week, her fiance, Jason Turkish, said he would vote for Rogers. Stevens then demanded that El-Sayed condemn an outside group’s ad that blamed Israel for high prices, and El-Sayed accused her of relitigating the primary. A planned joint church appearance with Rep. Jim Clyburn, D-S.C., fell apart after Rep. Debbie Dingell, D-Mich., asked Stevens not to attend. Stevens went to church with Rogers instead and endorsed him an hour later. Her chief of staff and her communications director both resigned.
The case that it’s an overreaction
Most of this was already priced in. The feud has been front-page news for a week, and Stevens’ fiance backed Rogers days ago. Traders who thought Stevens would cost El-Sayed votes had every chance to sell before Sunday. The market went up instead.
Endorsements rarely move votes. Political science research consistently finds that endorsements from other politicians have small effects on general-election vote share, especially when they cross party lines. Voters who care most about Stevens’ concerns on Israel had likely already heard them.
Much of the vote is already in. Michigan votes early and by mail in large numbers, and a Sunday endorsement can’t change ballots already cast.
The polls haven’t moved, because there hasn’t been time. El-Sayed led every recent public poll, by about 6 points in The Detroit News/WDIV poll and by 7 in CBS Detroit’s. Kalshi’s own margin market had him winning by about 2.8 points Saturday.
Political favorites are usually underpriced. A sharp late drop on a single headline is exactly the kind of move that has tended to fade.
The case that it’s not
Stevens’ voters are El-Sayed’s weak spot. She beat him in Wayne and Oakland counties in the primary, with strong support from Black and Jewish voters, two groups Democrats need in large numbers to win a close statewide race. Rogers deliberately chose a Black church in Detroit for the appearance.
It’s more than one endorsement. It comes on top of former Sen. Joe Manchin’s endorsement of Rogers and public criticism from Detroit civil rights leaders. The headline tells a story of Democratic division, and it lands in the final 48 hours, with no time to respond.
The 77- to 80-cent price may have been too high. A 3- to 6-point polling lead, given typical Senate polling error, works out to roughly a 70% to 75% chance of winning. Some of Sunday’s drop may simply be the market correcting a price that ran ahead of the evidence.
Our read
The drop is bigger than the news. A late endorsement from a rival is worth a point or so of vote share at most, which is roughly the difference between a 3-point lead and a 2-point lead. At 69 cents, El-Sayed is priced close to where his polls alone would put him, as if Sunday’s news cost him a little and nothing else happened. The market went from slightly overconfident to roughly fair, with a small lean toward value on El-Sayed.
This is not a lock. If Black turnout in Detroit comes in soft, Sunday will look like the moment the race turned. But the evidence that Stevens can move enough votes in 48 hours to flip a race in which her former opponent leads every poll is thin.
What to watch
- Any public poll taken after Sunday. A poll showing the race within 2 points would justify the move. One still showing a 5-point lead would not.
- Early and Election Day turnout in Wayne County. Turnout in Detroit is the clearest test of whether the endorsement mattered.
- The gap between Kalshi and Polymarket. Polymarket fell further. If the two venues settle at different prices, one of them is wrong.
- Whether the price drifts back by Monday night. Late overreactions in political markets have tended to fade as the vote nears.
Prices are from The Prediction Network’s Michigan Senate market as of Sunday afternoon, Nov. 1. Prediction markets are not guarantees. Trade responsibly.
