The Senate starts at 9 a.m., and at 10 a.m. it will vote on a motion to end debate on the House-passed budget resolution, the amended H.J.Res. 59.

Sixty senators are needed to end debate, and the votes are expected to be there. Seven Republicans have said they would vote to end debate, but others could join them, which would appear to mean the 60 votes are there.

A successful vote to end debate would start a 30-hour clock, which could be shortened to allow a final vote today. However, time would have to be yielded back by unanimous consent — if there's no agreement to speed up the process, a final vote would come on Wednesday.

Some GOP opponents, like Budget Committee ranking member Jeff SessionsJefferson (Jeff) Beauregard SessionsCurtis wins Chaffetz's former Utah House seat Overnight Cybersecurity: What we learned from Carter Page's House Intel testimony | House to mark up foreign intel reform law | FBI can't access Texas shooter's phone | Sessions to testify at hearing amid Russia scrutiny FBI can’t unlock Texas shooter’s phone MORE (R-Ala.), will likely want to spend some time on the floor arguing against the budget, which repeals some of the sequester and replaces it with new fees and other revenues.

But once the Senate votes to end debate, passage of the budget either Tuesday or Wednesday is certain, as it only needs a simple majority.

If the Senate can hold a final vote on the budget today, it will then hold another vote to end debate on the National Defense Authorization Act. That vote would set up another 30 hours of debate, which could mean a final Senate vote on this bill, the amended H.R. 3304, as late as Thursday or Friday.