"It's the economy, stupid," read a sign in Bill Clinton's 1992 campaign headquarters, reminding everyone that while the election may have looked like a contest between a dynamic young agent of change and a hidebound old establishment figure, the most important thing was to talk about the faltering economy as much as possible. That, they all understood, was what moved votes.

In the time since, few have contested the belief that except for extraordinary moments (like when there's a war on), no policy issue matters more than the state of the economy. Presidents get more credit than they deserve when it's good and more blame than they deserve when it's bad, and political scientists argue about whether GDP growth, income growth, or unemployment is the best predictor of the result of a presidential race, but they all agree that the economy will go a long way to determining who wins. Even in the years in between elections, the president's fate will be shaped by economic factors.

Or at least we thought so, until now. Our most unusual president may be severing the link between economics and political outcomes.

Republicans are seeing it play out in the special election in Pennsylvania taking place on Tuesday. They thought they'd be able to just remind voters of the tax cut law they passed in December and the race would be in the bag. After all, who can argue with more money in your paycheck? But after trying to promote their candidate by touting the tax cut, Republicans quietly dropped the issue after seeing it wasn't moving votes. Now they're going back to culture war appeals on issues like immigration — a much more Trumpian approach.

Back in Washington, the party is distressed that the tax cut hasn't proven more popular. They mocked Nancy Pelosi for saying it only gave "crumbs" to ordinary people while larding riches on corporations and the wealthy, on the theory that if a taxpayer's getting another $500 or $1,000 a year they won't care what Walmart or General Election was given. But that turned out not to be the case; people seem to care more about fairness than Republicans predicted, and the law's popularity remains underwater.

Then there's President Trump's approval rating. In an earlier time, we'd expect that a president presiding over an economy with 4.1 percent unemployment and strong job growth would be riding high, no matter what else he did. That's what saved Bill Clinton when he was impeached; if the economy wasn't in the midst of a boom, it seems unlikely that voters would have been as forgiving of his affair with a young staffer. But as it was, Clinton's approval was at 66 percent the week his impeachment trial ended.

No such luck for Trump. His approval ratings are stuck around 40 percent (sometimes lower), no matter how many good monthly jobs reports we get.

One might posit that voters aren't giving Trump much credit for the economy because it's doing about as well as it was before he took office. The last time unemployment was over 6 percent was in August of 2014, over three and a half years ago. It almost seems like it's been this way forever, with "this way" meaning that if you need a job you can find one, but it might not be the kind of job you want.

That's another part of this puzzle: People are keenly aware that "the economy" is more complicated than just jobs and growth. If a job doesn't come with benefits or security, you can have one and still not feel like the economy is serving you particularly well. We just watched public school teachers in Virginia stage a dramatic strike to get themselves a 5 percent raise, which at a median salary of $45,700 would mean a bump up to $47,985 — better, but still not nearly what they ought to be paid. With wages growing painfully slowly and inequality constantly increasing, it's hard for a few months or even years of job gains to convince everyone that we've entered a time of boundless prosperity.

And it's almost impossible to assess Donald Trump on the basis of any factor outside of Donald Trump. People might have been able to compartmentalize the Lewinsky matter, but every day in the Trump era features a half-dozen Lewinsky-level scandals. The president may have colluded with a hostile foreign power to get elected, he allegedly gave hush money to a porn star to cover up their affair, he's in an unending war with the news media, his staff is running for the hills, and each day we all wake up wondering what he's going to rage-tweet because of something he saw on Fox & Friends. In that reality it's awfully hard to say, "Sure, but what I'm focused on is durable goods orders for the second quarter."

But more than anything else, Trump has proven, and exacerbated, the power of polarization. For the economy to determine what happens in elections, there have to be a significant number of people who are willing to change their votes based on whether we're in a recession or a boom. That number was never large, but it's tiny today. Trump proved that even a bigoted misogynistic reality show buffoon wouldn't lose the support of the Republican Party, and it looks like we've entered a period where attempts at persuasion pale next to mobilization. No matter what's happening in the world, getting people to change their minds will be next to impossible; victory will go to the party that does the best job of getting its own voters to the polls.

That isn't to say that Trump could survive if there's a recession in 2020, or that he won't be helped if the economy is doing well. But the president gives us so many other things to worry about.