coaligarse

To form a coalition or join forces with others, typically in a political or strategic context — partidos que se coaligan para ganar las elecciones. A variant of the more common coligarse; both describe parties or groups formally allying.

• Los partidos de oposición se coaligaron para las elecciones. — The opposition parties formed a coalition for the elections.
• Varias empresas se coaligaron contra el nuevo impuesto. — Several companies joined forces against the new tax.
• Los sindicatos decidieron coaligarse para negociar mejor. — The unions decided to join forces to negotiate better.

Coaligarse and coligarse mean the same thing — both are correct, with coligarse slightly more common; don't assume they refer to different kinds of alliances.

Often confused with coligarse.