throw in one's lot with

throw in one's lot with or  {literary} cast in one's lot with  {v. phr.}

To decide to share or take part in anything that happens to; join.

The thief decided to throw in his lot with the gang when he heard their plans.

Washington was rich, but he decided to cast in his lot with the colonies against Britain.

When Carl was old enough to vote, he threw in his lot with the Democrats.

Syn.: JOIN FORCES.