Democratic Senate candidate Beto O'Rourke of Texas takes the stage at a rally in El Paso following his defeat to incumbent Sen. Ted Cruz. (Michael Robinson Chavez/The Washington Post)

Democrats didn’t win everywhere Tuesday night, despite their clear momentum. They won over the House and some governor seats, but they also lost seats in the Senate, making their path back to the majority there more difficult than it was before.

How could that be? Unfairness, of course.

Now that the results have rolled in, some have begun citing a so-called Senate popular vote. It goes like this: Democrats won lots more votes, but they somehow lost seats. Here’s a sampling:

MSNBC host Joy Reid even previewed such a circumstance, suggesting it would lead to a “legitimacy crisis.” It’s an argument that cropped up in 2016, too, amid a similar set of circumstances.

But the Senate popular vote is a bogus stat for a whole host of reasons. It’s true that the Senate isn’t set up particularly favorably for Democrats — there were 30 red states in the 2016 election and 20 blue ones, and the many small red states such as Wyoming have the same number of senators as exponentially more populous blue states such as California and New York — but the Senate popular vote is not a stat that tells that tale.

The biggest problem with it is that not every state is up for reelection, leading to a skewed picture. If more Democratic seats are up for reelection, it stands to reason that Democrats will do well in the popular vote. And that’s exactly what happened in 2018: Democrats were defending 26 states, and Republicans just nine.

The second reason is California. It has a unique system in which the top two candidates advance to the general election, regardless of party. This year, that was two Democrats. That means all 6 million votes counted (with many more to come) go to the Democrats. Given California is by far the biggest state, that badly skews the national “Senate popular vote.” And in fact, the exact same thing happened in 2016, which was a big reason it was a highly misleading stat then, too.

Let’s assume there are eventually 9 million votes in California’s Senate races. If we apply the results of Tuesday’s governor’s race — Democrats' 59.5 percent to Republicans' 40.5 percent — that would give Democrats 5.3 million votes and the GOP 3.7 million. If you alter the numbers from the first tweet above to include this very plausible partisan split in California, Democrats' national “Senate popular vote” edge would be reduced to 36.8 million to 35.2 million — a pretty even split.

But that’s not quite it. There’s also this: While Democrats lost seats on Tuesday night, they actually won most of the races that were held — at least 22 of the 35 seats, and possibly a couple more. That’s 63 percent or more of the seats, despite winning just 55 percent of the vote.

Sounds pretty unfair to Republicans, right?