Not necessarily; it only takes a one-vote margin to pass legislation in the House. Quite a lot of House races are on "auto pilot", politically--that is, there'

Not necessarily; it only takes a one-vote margin to pass legislation in the House. Quite a lot of House races are on "auto pilot", politically--that is, there's not much suspense about which party's candidate is likely to win. This is in part because of gerrymandering that produces districts favorable to one party vs another. Tiny districts would be like gerrymandering on steroids. It wouldn't take much fancy geometry to produce a map in which the vast majority of House races remain easily predictable. And it is the marginal (unpredictable) races that atract the bulk of the big spending.