Senate Majority Leader Harry Reid introduced the Senate version of the health reform bill on Wednesday, and tonight the full Senate is expected to vote on the "motion to proceed," which would clear the way for the Senate to begin debate on the bill. Sixty votes are needed to pass cloture on the motion, after which the bill would move to the floor for discussion.

CNN reports:

Proceedings got under way shortly before 10 a.m. Saturday and will last through the early evening.

Around 8 p.m., the Senate will hold a roll call vote on the motion to invoke cloture.

Reid needs 60 votes to overcome a certain GOP filibuster attempt and open the chamber's debate on the bill. It also would take 60 votes to close debate that could last for weeks, while final approval of the bill would require only a simple majority.