A political candidate who is both campaigning for public office, and complaining about another candidate campaigning for the same position.
Person A: "So what have you seen about that governor's race in Minnesota?"
Person B: "A whole lot of camplaining. One candidate was crying about yard sign placement. Another candidate was whining about comments they made being taken out of context. I can't wait for this round of elections to be over with..."
to engage in a negative, manufactured complain-based campaign against an incumbent officeholder.
Look at that idiot Kerry -- he's just camplaining.