President Trump participates in a Diwali celebration at the White House on Tuesday. (Jonathan Ernst/Reuters)

President Trump is in a sour mood — and apparently has been ever since his party suffered its worst House losses since Watergate last week. It started with him repeatedly snapping at reporters and continued during a trip to Europe, as The Washington Post’s Josh Dawsey and Philip Rucker report in their must-read new story:

As he jetted to Paris last Friday, President Trump received a congratulatory phone call aboard Air Force One. British Prime Minister Theresa May was calling to celebrate the Republican Party’s wins in the midterm elections — never mind that Democrats seized control of the House — but her appeal to the American president’s vanity was met with an ornery outburst.

Trump berated May for Britain not doing enough, in his assessment, to contain Iran. He questioned her over Brexit and complained about the trade deals he sees as unfair with European countries. May has endured Trump’s churlish temper before, but still her aides were shaken by his especially foul mood, according to U.S. and European officials briefed on the conversation.

For Trump, that testy call set the tone for five days of fury — evident in Trump’s splenetic tweets and described in interviews with 14 senior administration officials, outside Trump confidants and foreign diplomats, many of whom spoke on the condition of anonymity because of the sensitivity of the issue.

This is a marked departure from the man who, a day after the Nov. 6 election, declared it a “complete victory” for his party. You’d think a guy so pleased would show it. But his conduct in that same news conference, as I argued, betrayed how he really felt: defeated. And the results since then in previously undecided races have only gotten worse for Republicans.

Trump’s continued foul mood about the whole thing leads to this question: Is he surprised? What happened last Tuesday and has happened since then has been very much in line with almost all of the projections. The national polls were largely right on the money, and the House had been expected to flip Democratic for months.

But for months Trump publicly doubted all that. He said there was a “red wave” coming — not a blue one. He said his party would do very well in the Senate. He regularly touted Rasmussen polls that showed his approval rating around 50 percent or higher. That pollster showed Republicans on the eve of the election with a one-point edge on the generic ballot — a finding drastically different from all the other pollsters, and one that would badly miss the actual result. (Democrats currently lead by seven points in the national popular vote, and that lead is going to grow thanks to California’s slow ballot-counting.)

Trump has some reason to doubt the polls. Some pollsters in key states in 2016 badly missed, leading us all to undersell Trump’s odds of winning — a circumstance that has led to plenty of soul-searching for people in this line of work. But the national polls were largely spot-on.

There is a tendency with Trump to believe that he says things like this for strategic reasons — that he knows what he’s doing when he tries to inflate his political prowess. But as with his myriad falsehoods and conspiracy theories, there’s another option: He has crafted his own reality, which is significantly rosier than actual reality. There was really no reason for Trump to suggest a red wave, given how divorced from reality it was, and it actually risked being counterproductive. GOP consultants worried it would give Republican voters a false sense of security and hurt turnout. But Trump kept saying it. While they were lowering expectations just before the election, he declined to join them.

And we’ve occasionally seen what it looks like when well-acknowledged reality catches up with Trump — apparently to his great surprise. Speaking at the United Nations General Assembly in September, he decided to slip in his far-fetched claim to having accomplished more at this point in his presidency than almost every previous president. The assembled world leaders literally laughed, and Trump seemed genuinely taken aback by that. “Didn’t expect that reaction,” he said, “but that’s okay.”

Earlier in his presidency, Trump also seemed taken aback when a reporter pointed out he was using a false statistic about the size of his electoral college victory — even though that number had been fact-checked as false many times before. “Well, I don’t know,” Trump said, “I was given that information.”

Trump’s mood could be about other factors, like internal White House turmoil, or it could be about the fact that he now has to contend with House Democrats using their majority to investigate him. But according to Dawsey and Rucker, the election continues to be a source of frustration. Trump has also fixated on the Senate race in Florida, lodging conspiracy theories and alleging Democratic foul play without providing evidence.

The totality of it suggests he wasn’t exactly prepared for this outcome, which he really should have been. Perhaps he truly believed he was a popular president prepared to shock prognosticators again. Maybe he really thinks his approval rating among African Americans is 40 percent, even though there’s no conceivable way that’s true.

As indicators of how insulated from reality he often finds himself, it’s a pretty good case in point.