I still wouldn't call it rigging, because it IS legal. It's more like influencing in a legal manner.
Is it fair? No, but it's legal, so it's NOT rigging, by definition. It's the same with the Electoral College. There are ways to manipulate it, and they aren't specifically illegal, so it's not rigging.
Make gerrymandering and Electoral College illegal, and then manipulating them would be rigging.