At this point, Democrats look certain to take back the House. But due to geography and gerrymandering, their majority in the chamber will fall far short of their majority at the polls.

As I write this, the New York Times is projecting that Democrats will win the House popular vote by more than 8 percentage points. If that margin holds, it will be the largest since the Democrats’ 2008 victory, which came amid a collapsing economy, a hideously unpopular war, and the rise of Barack Obama’s massive grassroots army.

Unemployment is at 3.7 percent right now. The economy is growing. For the country to vote this decisively against the incumbent party is shocking. Midterm election results hinge on turnout, gerrymandering, and the specific set of Senate seats in play, so they’re not a clear picture of the national mood. But for the House popular vote to swing this hard against Republicans under these economic conditions reflects a profound political failure on Donald Trump’s part. Republicans are paying the Trump tax, and it’s getting larger.

Let me back up. In 2016, Vox worked with political scientists to build an “ensemble model” that combined the best presidential forecasts, weighted them by past accuracy, and updated them with new information.

That model said the baseline expectation was that the Republican nominee — whoever it was — was favored to win the 2016 election. The exact prediction was that the GOP’s candidate would capture 50.9 percent of the popular vote.

Trump was polling far beneath that. He was underperforming what should be expected of the Republican nominee, given the state of the economy and President Obama’s approval ratings. This was interesting. There’d been a lot of discussion in 2016 about how bad a nominee Trump was, but this was a way to roughly quantify it.

Through the final months of the election, we tracked the difference between where Trump was polling and where our model suggested he should be polling and called it “the Trump tax” — it was the penalty Republicans appeared to be paying for nominating Donald Trump, rather than a different Republican. It wasn’t huge, but in a closely divided country, it was big enough to matter. On the eve of the election, it was 3.8 points.

Trump, of course, unexpectedly won the Electoral College, and thus the presidency. But he won far less than 50.9 percent of the two-party vote. It’s likely that Marco Rubio or John Kasich would’ve won the election convincingly. And if you believed Hillary Clinton was an unusually weak Democratic candidate, as many did (and as polls suggested), then Trump’s underperformance was even larger than our measure indicated.

With Trump, two contrary ideas need to be held simultaneously: His rise to the presidency was a remarkable political achievement by any measure, and yet he is substantially less popular than a politician in his position should be. He’s a political genius and a political underperformer, all at the same time.

Since winning office, Trump has been buoyed by a strong economy. The trends predate him — job growth during the first two years of his presidency has been slightly slower than in the two years preceding his presidency — but their cumulative effect is undeniable: We’re enjoying the longest economic expansion in American history, we’re at or near full employment, and Americans tell pollsters they’re more optimistic about the economy than at any point in decades.

Nothing predicts presidential popularity like a strong economy. And yet in November 2018, Trump is less popular at 3.7 percent unemployment than Obama was in November 2010, when unemployment was 9.8 percent. That’s a tremendous political failure, and it should be seen as such.

Trump’s continued political survival is so unlikely that he’s often graded on a steep curve. It’s like watching a dog make pancakes: Who cares if the pancakes are good? When his stratagems work, or simply seem to work, he’s heralded as a genius. When they don’t, he rarely absorbs the blame another politician would face.

Imagine the election had gone another way. Imagine Trump’s hyping of the migrant caravan had succeeded, and Republicans had outperformed expectations. Trump would be heralded as a mastermind, and fearmongering on immigration would be the path forward for Republicans.

The opposite judgment should land with just as much force. Trump’s decision to keep the country in a constant state of agitation and his critics in a constant state of mobilization has failed. His effort to use immigrants to scare Americans rather than touting the economy to unite them lost the House. Republicans, rather than reaping the rewards of a booming economy, are facing a blistering electoral repudiation. The only reasons their losses are contained is that gerrymandering and geography have tilted the map in their favor, and so, like Trump himself, the share of power they win obscures how badly they lag Democrats in vote totals.

Republicans, increasingly, wield power only because America’s political system insulates them from the public’s judgments. The leader of their party — and of the country — came in second in the popular vote to Hillary Clinton and, despite a roaring economy, hasn’t cracked 50 percent in the polls since taking office. Tonight, Republicans lost the House, and if Democrats hadn’t been defending 26 Senate seats to Republicans’ nine, it’s likely they would’ve seen a rout in the Senate too.

The GOP needs to ask itself: What’s going to happen in 2020, when the Senate map reverses, and Republicans are defending twice as many seats as Democrats? What if unemployment is 5.7 percent rather than 3.7 percent?

That Republicans performed this poorly amid this strong an economy and this much geographic advantage should be a wake-up call to the party. Trump’s political strategy is failing, and they are paying the cost.