[OldMissileer]

Do they define a quorum based upon both parties being present, or based on numbers?

I do not know. I thought it may have been based on party affiliation as well as numbers but I got a comment from a poster who looks like a local and he implied it was numbers.

[PapaBear3625]

I looked at the Wisconsin constitution. It requires a 3/5ths quorum. The Senate consists of 19 Rs and 14 Ds, which is 34 total. They need 20 to make 3/5ths, so they need one of the Ds to show. If they had 20 Rs and 13 Ds, they would not need any dems at all, which points out how important each single seat can be.