A tweet from MSNBC’s “Morning Joe” summarized the dramatic shift seen in Orange County, Calif., politics in the 2018 election. Two years ago, following the election of President Trump, most of the county was represented in the House by members of the Republican Party. As of Friday morning, after the race in California’s 45th District was called for Katie Porter (D), and with Gil Cisneros (D) taking a hard-to-beat lead in the 39th, the “Morning Joe” map is now solidly blue.

That map is misleading, because it doesn’t show the 38th District, a sliver of which overlaps with the county. In fact, Democrats now control all seven seats that overlap entirely or in part with the county.

How unusual is that? Quite. The last time that all of Orange County was represented by Democrats, there was only one district in Orange County. By the 1942 election, the sole district was held by a Republican. That was the case for 20 years. In 1962, the county got another district, and the two seats were split. Every 10 years, the districts were redrawn to fit the most recent Census data; every 10 years, the Republicans held most of the seats.

Notice, though, that this shift in Republican control is not entirely sudden. In the 2002 elections, the Democrats won the then-47th District. Ten years later, they controlled three. Now, all seven.

That shift mirrors the county’s record in presidential voting. One reason that Orange County was being watched closely on election night this year was that it, for the first time in 80 years, had backed the Democrat over the Republican in the presidential race. Not only that, but the county also voted more heavily Democratic than the nation on the whole, something that it didn’t do in the landslide 1936 contest.

Solidly Republican, birthplace of Richard Nixon — and then, starting in the 1980s, consistently less so. It wasn’t the 2018 election that turned Orange County blue, really. It was time.

So what changed? Well, for one thing, the demographics did.

In 1980, the county was 78 percent non-Hispanic white. Fewer than 300,000 Hispanic people lived there, along with another 100,000 or so people of Asian descent. Both of those latter populations grew as the former declined. By 2010, the county was majority-minority, and nearly as many Hispanic people lived there as whites.

The change in the demography of Orange County can be seen more readily if we look at the change as a percentage of the population in 1980. The Hispanic population soared; the white population eroded.

This is not, as we’ve noted before, a necessarily correlated pattern, the decrease in the white population and the increase in Democratic political support. But here the correlation is pretty clear, looking at the elections closest to each Census.

Losing every seat in a traditionally red county isn’t great for the Republicans, certainly. But the possible reason for getting shut out — a demographic shift that’s happening across the United States — may be worse news for them over the longer term.