1 informal the practice of exchanging favours, especially in politics by reciprocal voting for each other’s proposed legislation:they have gained leverage on Capitol Hill by a talent for political logrolling
[from the phrase you roll my log and I'll roll yours]
2a sport in which two contestants stand on a floating log and try to knock each other off by spinning it with their feet.
logrolling in other Oxford dictionaries
Definition of logrolling in the US English dictionary