2026 Democratic nominee for US Senate in Iowa?

Prediction market on manifold. Chuck Grassley (R-IA) is up for reelection in 2026. Which Democrat will face him? (Feel free to suggest additions, though I'll only add people who I subjectively think have a >2% chance of winning.)

24h Volume: $50. Liquidity: $1,000. Resolves: 11/3/2026.