It doesn't necessarily have anything to do with gerrymandering (though it likely does to some extent). A more likely cause is that cities tend to have a democra

It doesn't necessarily have anything to do with gerrymandering (though it likely does to some extent). A more likely cause is that cities tend to have a democrat win by a wide margin and rural areas tend to have a republican win by a smaller margin. Combine that with the fact that all districts aren't identical in size and you get a legitimate way for this to happen.