To make common cause with

to join with in purposes and aims.
- Macaulay.
to join or ally one's self with.

See also: Cause, Common

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
The MQM needs to understand the complexities in Sindh and should expand to interior Sindh and make a serious effort to make common cause with an average Sindhi who had been left in the dark ages, while all the development was undertaken in urban Sindh.