throw in one's lot with
• decide to ally oneself closely with and share the fate of (a person or group).
• "the bourgeoisie had thrown in its lot with the monarchy"
Similar:
join forces with,
join up with,
form an alliance with,
ally with,
align oneself with,
link up with,
go into league with,
combine with,
join fortunes with,
make common cause with,
