The measure would essentially limit debate on a waiver that is needed in order for retired Gen. Mattis to serve as secretary of defense.
Under current law, the Department of Defense cannot be run by an individual who has served in the military in the last seven years. The waiver would allow Mattis to serve in that role even though he has only been out of the military for three years.
The spending bill does not automatically approve that waiver, it only limits the amount of time senators have to debate it to 10 hours. It will still take 60 votes to approve. But the expedited process could still save precious time in the Senate as lawmakers are expected to be busy in the new year installing the rest of Trump's cabinet, repealing the Affordable Care Act and getting a jump start on the appropriations process.
What makes Mattis so unique is that unlike the other cabinet positions, which only require a simple majority vote after Democrats voted to change the rules on presidential nominees in 2013, the waiver required to approve Mattis still needs 60 votes to pass, essentially making him subject to a 60-vote threshold.
While many Democrats warned Republicans about including the Mattis provision in the spending bill, it's not immediately clear if they will risk shutting down the government over it.
Lawmakers are in a rush to get the continuing resolution passed by Friday and head home for the holidays.