Supporters cheer for Republican presidential candidate Donald Trump as he arrives for his rally at the Charleston Civic Center on May 5, 2016 in Charleston, W. Va. (Mark Lyons/Getty Images)

At a rally for President Trump in West Virginia on Thursday night, the state’s governor is expected to make an unusual announcement: He’s bailing on the Democratic Party and becoming a Republican.

The announcement is unusual in the sense that governors don’t generally suddenly switch political parties. But it’s not that unusual for Gov. Jim Justice himself, who flipped from the Republican Party to the Democrats only two years ago.

Nor should it really be a surprise. With a few caveats, no governor in the past century has led a state that voted against his ostensible party so overwhelmingly in the prior year’s election as West Virginia’s Justice.

It’s not at all uncommon that a state will vote for a presidential candidate from one party and, the next year, find itself led by a governor of the other party. By our count, it’s happened over 450 times over the last 100 years, an average of 17 states in each election cycle. That’s skewed by a few blowout elections that saw a majority of states vote for one party even though their governor the following year was of the other party. But: not uncommon.

Nor is it that uncommon in recent years for a state to overwhelmingly vote for a candidate of one party but be governed by someone from the other. Here’s every time there’s been a gap between presidential vote and the governor the next year since 1916:

(We used the following year to account for governors elected alongside the presidential candidate.)

There have been four governors since 2004 who were way out of step with their states.

  • Dave Freudenthal (D) was governor of Wyoming when the state voted for George W. Bush in 2004 by a 38-point margin.
  • Linda Lingle (R) was governor of Hawaii when the state backed native son Barack Obama by 45 points in 2008.
  • Jim Douglas (R) was governor of Vermont when Obama won the same year by 37 points.
  • Last year, West Virginia voted for Trump by 42 points.

But there’s another way to look at the same data. Bush and Obama both won the popular vote those years. Trump didn’t. So, relative to the nation on the whole, those margins of support for Bush and Obama really weren’t that extreme. Sure, Obama won Hawaii by 45 points in 2008, but he won nationally by 7 points, so Hawaii was only 38 points more pro-Democratic than the country on the whole.

By that metric, Justice stands out. West Virginia not only voted for Trump by a wide margin, the country on the whole preferred Hillary Clinton by a narrow margin. So relative to the national mood — a consideration that you’ll notice smooths out those landslide elections — no governor in at least a century has seen his state vote against his party to the extent that Justice did.

The only governors that are close are also Democrats in states that voted Republican: Former Utah governor Scott Matheson in 1980 and former South Carolina governor Donald Russell in 1964. Otherwise, no Democrat or Republican has been more out of step from his state than Justice since at least 1916.

Given that Justice also doesn’t feel any strong ties to the Democratic Party, this flip seems, in retrospect, all but inevitable.