I would be surprised if it is higher than 10%

This is exactly how numeric markets work now, you could have used one of those (just FYI :))

I think the percentage of Republican votes is a more meaningful number at a glance though

47 Republicans ended up voting for it (along with every Democrat)

https://www.insider.com/47-republicans-vote-in-favor-bill-protecting-same-sex-marriage-2022-7

Resolves via PROB to # of republican YEA votes for the Repsect for Marriage Act / 211 (number of republican congressmen) * 100%

https://thehill.com/changing-america/respect/equality/3564442-house-to-vote-on-respect-for-marriage-act-in-response-to-clarence-thomas-opinion/

Play-money betting