Trump’s party is not at home on this ground and can’t play on it. Trumpians just want to wall it off. “DC should annex NOVA and return the governance of Virginia to Virginians!” Jerry Fallwell Jr. tweeted, referring to Northern Virginia, after the election results.

Populism has made the Republicans a rural party and given the Democrats everything else. In Virginia, Democrats won by a landslide among anybody who grew up in the age of globalization. Among voters 18-29, they won by an astounding 69 to 30 percent. Among voters 30-44, they won by 61 percent to 37 percent.

We could be seeing the creation of a new Democratic heartland, exurbia, and this alignment could hang around for a while. The stain Trump leaves on the G.O.P. will take some time to wash away. But this is bigger than Trump; it’s an alignment caused by the fundamental reality of the populist movement.

But does this mean Democratic dominance is baked in the cake? Here I would say, not so fast. It’s worth remembering that the Democrats don’t quite deserve this victory. It didn’t come about because of some masterly Democratic strategy. The Democrats won because the Republicans decided to shrink their coalition.

And it’s worth looking around the world and noting that center-left parties are in decline across Europe and beyond. These parties have lost touch with working class voters and are finding they can’t simply replace them with a mixture of identity politics and faculty lounge populism. What we’re seeing around the world is not the rise of left-wing dominance but the decline of major parties and the fragmentation of political parties across the board.

The crucial question going forward is what will the Democrats do? Will they make places like Loudon County their heartland, or will they amputate themselves the way the Republicans did, and retreat back to the cities?

Here’s how you can tell which way the Democrats are going. If they talk mostly about oligarchy and rich financiers, they are retreating to their base. But if they talk about mobility — geographic mobility, economic and social mobility, intellectual and spiritual mobility, they are talking the language of the suburbs. And if they have practical plans to enhance universal mobility, the age of Democratic dominance will be at hand.