Bedfellow:

noun

an associate or collaborator, especially one who forms a temporary alliance for reasons of expediency:

Politics makes strange bedfellows.
I remember some WW2 propaganda that has always stuck with me. It was the image of a Russian soldier running and leaping into bed with Uncle Sam and a British soldier. I was still a child sneaking Time Life books, so I smirked at the unintended(?) homoeroticsm of Uncle Sam and big strapping masculine soldiers in bed together. Despite my initial juvenile sexual humor, the larger implication wasn’t lost on me.

“Our new bedfellow!” the poster proclaimed, reminding Americans that the war had shifted. Russia was on our side. The Nazis were still evil, but the Russians had seen the light, come to Jesus, and suddenly loved American liberty. They were our friends and allies. Sort of. 

This image has always stayed with me, and even as an adult I recall it when I see groups at polar ends of…