I doubt it's really unique since it's such an obvious way to formalize "I will vote for your favorite piece of legislation if you vote for my favorite piece of

I doubt it's really unique since it's such an obvious way to formalize "I will vote for your favorite piece of legislation if you vote for my favorite piece of legislation" horse trading. Of course you can also do it informally by keeping track of which votes pass and which fail and then holding a grudge whenever one side isn't holding up their end of the bargain.