2028 Democratic Nomination — Cross-Exchange

The 2028 Democratic nomination is the deepest durable book in prediction markets: $390,280 a day on Kalshi against $54,434 on Polymarket, with more than 4 million contracts of open interest on each of Kalshi's leading legs. The first primaries are more than a year away. The book trades anyway.

The lead has changed hands on Kalshi. Jon Ossoff is now first at 16.5%, with Gavin Newsom and Alexandria Ocasio-Cortez level at 13.5%. Three weeks ago AOC led at 17% and Ossoff was third at 14%. Polymarket has not followed all the way: AOC 16.75%, Newsom 16.05%, Ossoff 15.45%, three names inside a point and a half. Manifold sides with Kalshi's order, Ossoff 17.3%.

The flow has moved to the leaders. Ossoff took $41,053 on Kalshi and Newsom $22,358; Andy Beshear, who carried twice the favorite's volume in September, took $7,895 and has risen from 3.8% to 5.85%.

The exchanges still disagree on levels: Polymarket prices AOC three points richer than Kalshi and Newsom two and a half points richer.

Kalshi and Polymarket run the same question at seven times the size on Kalshi. Read them side by side: the same three names lead both, in a different order. Kalshi has Ossoff first; Polymarket has AOC first and Ossoff third.

Alexandria Ocasio-Cortez priced directly on each side. 13.5% on Kalshi against 16.75% on Polymarket—a three-point spread that has held while both prices fell, from 17% and 20.1% three weeks ago. She still leads on Polymarket; on Kalshi she is level with Newsom behind Ossoff. Kalshi's leg carries 4.68 million contracts of open interest.

Newsom at 13.5% and Ossoff at 16.5% on Kalshi. Ossoff's climb is the structural change in this book since spring: a first-term senator from a state that has flipped twice, now priced ahead of every other name on Kalshi. He also took the day's largest flow, $41,053, nearly twice Newsom's $22,358.

Andy Beshear took $138,380 in a day at 3.8% three weeks ago, more than the top three legs combined. The price has since followed: he is 5.85% on Kalshi and fifth in the book, and his volume has fallen back to $7,895.

Polymarket shows the same move in miniature, Beshear up from 2.2% to 3.15% on $6,485, more than AOC's $4,632. When two independent books put outsized flow on the same longshot, that is usually accumulation rather than noise, and here the price moved after it.

Adjacent books that extend the story. The Democratic VP nomination trades at $1,316 a day, with Elissa Slotkin at 8.6% and AOC at 8.55% on top. Manifold runs an independent nominee book worth reading as a crowd check against the two big exchanges: it has Ossoff first at 17.3%, Newsom 15.3% and AOC 14.7%, the same order as Kalshi.

• Ossoff in first on Kalshi is the real move. 16.5%, three points clear, and third on Polymarket at 15.45%. His 2026 Senate re-election in Georgia, a month away, is the event most likely to reprice this leg in either direction.
• The exchanges disagree on the leader. Kalshi and Manifold have Ossoff; Polymarket has AOC by seven-tenths of a point over Newsom. Watch which venue moves.
• Beshear's price caught up with his flow. 3.8% to 5.85% on Kalshi in three weeks. Whether the accumulation resumes at the higher price is the next read.
• AOC's three-point cross-exchange spread is durable. 13.5% on Kalshi against 16.75% on Polymarket; both have fallen about three and a half points and the gap has not closed.
• Nothing here settles for two years. The open interest, over 4 million contracts on each of several legs, means holders are financing multi-year positions, which is itself a signal about conviction.
• Watch the 2026 midterms as the first real information event. Senate outcomes in Georgia, Michigan and North Carolina reprice several of these names directly; a bad night for the party reprices all of them.