cast lot with

cast your lot with somebody/something

to choose to share in whatever happens to another person or a group If I'm going to cast my lot with this team, I'm going to try to make them as good as possible any way I can.
Etymology: based on the literal meaning of cast your lot (to throw dice or other objects as a way of deciding what will happen)
See also: cast, lot

cast (one's) lot with

To join or side with for better or worse.
See also: cast, lot