From the first years of a century already one-fifth completed, we’ve been told that a new, ascendant America — more nonwhite, more culturally liberal, more feminist — was going to dominate our politics for years to come.

Those predictions have, partially, come true. Barack Obama was elected and reelected president in 2008 and 2012, and Democrats won majorities in House contests in 2006, 2008, and 2018.

But those are slimmer pickings than the emerging majorities were promised. And President Trump’s victory in 2016 has made a mockery of the predictions. He wasn’t ascendant America’s choice. Like (but no more so than) other Republicans, he ran way behind among nonwhites. From millennials and Generation Z, he evokes, “OK, boomer.” Feminists feel queasy at the mention of his name.

Demographics, it turns out, don’t automatically turn into destiny. Ascendant groups’ triumphalism can coalesce those with opposite values into unaccustomed unity and enthusiasm. Ascendant leaders, not cautioned by sympathetic media, can concoct extreme policies (Green New Deal, anyone?) unsellable to most voters.

And perhaps ascendant groups, with their low birth rates, may not become as ascendant as demographers expected.

That’s a conclusion you might draw from the Census Bureau’s state population estimates for mid-year 2019, released just one day before the year-end deadline. They’re the best leading indicator we’ve got for the 2020 census, whose results will reapportion the House of Representatives and the Electoral College.

Reapportionment, it appears, would work to the advantage of Trump, were it done before the 2020 election — the 30 states he carried in 2016 seem likely to gain three congressional seats and electoral votes.

One reason is that California, for the first time since it was admitted to the union in 1850, is gaining population at a below-national-average rate and is projected to lose a House seat. The nation’s largest state seems stalled at just below 40 million people, with international migration just barely outbalancing a net domestic outflow of 912,000 over the decade.

Texas, the No. 2 state, is growing far more robustly, from 25 million in 2010 to almost 29 million this year. That’s a bigger percentage gain over nine years than in any other state except big-family-size Utah. Florida, which passed New York to become No. 3 in 2013, gained 14%. A decade ago, it trailed New York by half a million. Now, with 21 million, it’s 2 million ahead.

These changes favor Republicans. Some upscale Texans trended Democratic in 2018, and perhaps some incoming Californians might import the left-wing politics whose results spurred their migration, as in Colorado and Arizona. But Texas’s middle-income Latinos and high-education whites remain much more Republican than their California counterparts.

Florida, though attracting more international immigrants than California and more domestic in-migrants than Texas, is nevertheless trending Republican. Domestic newcomers tend to be Trump-friendly — Catholics fleeing the high-tax Northeast and small-town Midwesterner retirees fleeing the cold. Incoming immigrants and Puerto Ricans seem amenable to Republican policies, and Hispanics and blacks join in giving Republican Gov. Ron DeSantis’s job approval more than 60%.

With Texas projected by Polidata, Inc. to gain three electoral votes and Florida two, together they should outvote California by 72 to 54 electoral votes, compared to 67-55 this year.

Working for Democrats is the perceptible southward migration of blacks from ailing northern cities such as Chicago to southern boom metros such as Atlanta. But fragmentary poll results suggest some blacks, especially young, middle-class men, may also be moving Trumpward, perhaps recoiling from policies that have produced high crime and stagnant economies in the cities they chose to leave.

In the early 2010s, there was notable population growth in the central cities that have become almost unanimously Democratic. But that trend has now been reversed; even New York City, after six years of Bill de Blasio, is losing people.

That leaves Democrats, however ascendant they may feel, with the psephological disadvantage of having their votes heavily concentrated in low-growth metro areas while opposition voters are more evenly spread out over the faster-growing remainder of the country.

A party in that situation has two choices. One is to change the rules, but amending the Constitution is hard, and finagling to undercut the Electoral College likely won’t work.

The other choice is to extend your appeal beyond your 80%-plus strongholds in central cities, university towns, and suburbs favored by Ivy League graduates. Democrats had some success doing this in 2018. But their presidential candidates, seeking Democratic primary votes, seem less interested so far this year.

Relying exclusively on “ascendant America” is not a sure-to-lose strategy. Hillary Clinton, despite her disdain for “deplorables,” nearly won. But, as Trump shrewdly discerned (or stumbled into discovering), it’s not a sure winner either.