United front
In Leninist theory, a united front is a coalition of left-wing working class forces which put forward a common set of demands and share a common plan of action, but which do not subordinate themselves to the front, retaining their abilities for independent political action and continuing to hold different political programmes.
The Stalinist theory of a popular front was somewhat different, because it could include bourgeois forces like liberals and have a minimum set of demands put forward, with the more militant demands of communist groups being hidden or sublimated in that effort.
Both tactics have seen successes in particular situations (like the fight against fascism) as well as massive failures (among them the assassination of Salvador Allende) over the course of the 20th Century.