https://insightprediction.com/m/94410/which-2022-senate-race-will-be-the-closest

This market will resolve positively to the bracket containing the 2022 US Senate race that has the smallest margin of victory (percentage difference) between the first and second place candidates. For races utilizing RCV, the published popular vote counts for the final round will be used. If any election results in a runoff or secondary election, then the results of the runoff will be what is considered for this market.