What does a new Democrat-dominated party system look like?

[clever but short]

I think largely it would involve gaining a lock on the demographics already trending Democrat, that is suburban white voters, and enormous margins with younger voters who will become a larger part of the electorate as they grow older. Geographically I think a key election to look at would be Alabama Senate 2017. Counties like Tuscaloosa and Madison would have to be consistently (non-Atlas) blue, and minority turnout would have to be consistently high. For Democrats to actually dominate a party system like this, results like in Alabama would need to be a consistent thing in other now reliably red states. Counties like Tulsa OK and Greenville SC would have to flip, with Republicans really having any standing only in white rural areas.

Of course this is all hypothetical. The counterpoint for Republicans would be to look at Charlie Baker and Larry Hogan win maps in Massachusetts and Maryland. Essentially it boils down to if either party can completely win over white suburban voters, then that party would dominate.