Bet the under 52 seats held by Republicans on Jan 29 at Pinnacle. All calculations point to at best 52 seats with a lot of plausible ways for 51 or even 50 seats held. Chances of 53 or more are looking very slim, so you basically are freerolling unless some very big developments occur. The Presidential election is a bunch of things rolled up into one, but the Senate races are all getting defined early and won't be as subject to sudden swings in voter sentiment.