The two largest railroad unions, Brotherhood of Locomotive Engineers and Trainmen (BLET) and the International Association of Sheet Metal, Air, Rail, and Transportation Workers (SMART-TD) took separate tacts with their votes to ratify a contract with freight railroads on Monday. BLET voted to ratify the contract, while SMART-TD rejected the contract.

A strike could happen as soon as Dec. 5 after the first cooling-off period ends for the 12 involved unions. That leaves a short window after the Thanksgiving recess for lawmakers to avert a work stoppage that could cost the economy billions per day. Major industry groups have expressed concern that rail industry cost cuts have hurt service and have been calling on President Biden and Congress to intervene to prevent a strike ahead of the holiday season.

However, the threat of congressional involvement, especially with Republicans poised to take over in the House, could force the unions’ hands. Republicans say they’re ready to require recommendations made in August by a board appointed by President Biden that didn’t go as far to improve working conditions as the unions wanted. That means unions that have since negotiated better deals could see their gains taken away. Read more here.