A lot of people had sky high expectations for the GOP in the Midwest because we thought Trump was going to go full European big government cultural conservative. The libertarians held their ground much better than expected circa 2017, meaning that Republicans also held their ground better than expected in the South/West but actually lost some ground in the North.
My guess is that some states that either party made a run for will become part of the base while others will snap back. Just like how Democrats made a run for Colorado, New Mexico, Nevada, Virginia, and Florida, some of them are now fairly blue and others are becoming more conservative. For Republicans, they looked for the Great Lakes, and to a smaller extent, the Northeast. Republicans definitely snagged Ohio, Iowa, and perhaps even Wisconsin... but it looks like Michigan and Pennsylvania are snapping back.
