Here is a representative take on the 2019 election from Ron Brownstein, highlighting the movement of the suburbs away from Trump and the GOP.
“When Trump was elected, there was an initial rejection of him in the suburbs,” says Jesse Ferguson, a Virginia-based Democratic strategist. “We are now seeing a full-on realignment.”
In that way, the GOP’s losses again raised the stakes for Republicans heading into 2020. In both message and agenda, Trump has reoriented the Republican Party toward the priorities and grievances of non-college-educated, evangelical, and nonurban white voters. His campaign has already signaled that it will focus its 2020 efforts primarily on turning out more working-class and rural white voters who did not participate in 2016.
But yesterday’s results again suggested that the costs of that intensely polarizing strategy may exceed the benefits. Republicans again suffered resounding repudiations in urban centers and inner suburbs, which contain many of the nonwhite, young-adult, and white-collar white voters who polls show are most resistant to Trump. If the metropolitan movement away from the Trump-era GOP “is permanent, there’s not much of a path for Republican victories nationally,” former Representative Tom Davis of Virginia, who chaired the National Republican Congressional Committee about two decades ago, told me."
This is fine as far as it goes but it's important to stress that the battle for the suburbs is not over. The battle will continue into 2020 and is likely to be decisive to the outcome. That's because the suburbs where the Democrats have been cleaning up tend to be suburbs that are fairly close to the city--"inner-ring" suburbs. But beyond the inner ring suburbs lies a vast amount of suburbia--"outer ring" suburbs, where the Democrats are not doing so well.
Robert Gebeloff explains in an excellent piece in the New York Times, where he analyzes all census tracts in the US and categorizes them on a 1-10 scale based on population and development density.
"We categorized the tracts that scored 1 or 2 as rural, and those that scored 9 or 10 as urban.
Everything in between was suburbia, although we eventually divided the suburbs into two groups as well. The reason? When we started running the numbers for demographics and 2016 election results, we realized that the more-dense suburban tracts were, as a group, far different from the less-dense tracts.
We called less-dense suburbs “outer ring,” and denser suburbs “inner ring.”...
[T]here is [a] distinction within the suburbs. All of suburbia has grown more diverse, but inner-ring neighborhoods have a much higher share of nonwhite residents than outer-ring neighborhoods do.
And the inner ring is more likely to support Democratic candidates; the outer more likely to vote Republican. Our analysis jibes with what some others have pointed out, there is a relationship between density and political preference.
“Majorities tend to flip from blue to red roughly where commuter suburbs give way to ‘exurban’ sprawl,” wrote Will Wilkinson, a researcher at the libertarian Niskanen Center, in a recent report. “That’s where the political boundary of the density divide is drawn.”
If 2016 is an indication, the battle lines are clear for 2020. Hillary Clinton dominated the inner-ring suburbs, and Donald J. Trump was dominant in the outer ring."
Where exactly the line in suburbia is drawn between Democratic and Republican strength will probably determine the outcome in 2020.