I'm still confused here. It seems to me that only a majority needs to be present, and the Dems are not needed for a quorum.
Another interesting section is Senate Rule 95. It holds that rules may not be changed without the consent of 2/3 of the members present. It seems to me that the Repubs could have a lot of fun here if they declared a quorum (majority of members, all R) and started making rule changes that would upset the Dems.
The Rule 89 I was looking at deals with the Sergeant At Arms going after absentees who are AWOL. Seems to me that could apply here :)