If you look at the history of it, the gerrymandering effort began with state legislative races, and focused in a few key states they hoped to flip republican. It was a cheap investment to sway small local state rep races, and they swung that to bias at a national level. And sure, started trying it in other states after that.
The really sad part of this is the Dems seeming inability to muster any organized response from a majority (but losing) position.
