Reagan rode an economic rebound, while Bush stumbled after a slump sent unemployment up to nearly 8 percent the summer before the election. Clinton had rapid economic growth, and Obama could claim a slow and steady recovery from the Great Recession. Run with the growth side of a business cycle and you have a path to re-election; hit a downturn and your chances shrink accordingly.

Trump is on the growth side of a business cycle. It’s not as robust as past expansions, but unemployment is low and, crucially, wages have increased, however slightly. Seventy percent of Americans say the economy is either “excellent” or “good,” although only 41 percent say he deserves credit. It’s his behavior — the lies and the prejudice, the corruption and the incompetence — that has made him unpopular, and kept him far below the typical president with economic growth on his side.

Will this hold? Will Trump claim the benefits of a strong economy, or will his actions and behavior leave him on the wrong side of the public and on the path to defeat?

Pollsters may have missed key signs of a Trump victory like his late surge in the Rust Belt, but most political science forecasts of the 2016 presidential election were close to the mark. Of 10 forecasts made between late June and early September, all but two came within roughly 2 points of the final two-party national popular vote. One of them, the Time for a Change model from the Emory University political scientist Alan Abramowitz, undershot Hillary Clinton’s share of the vote but predicted, correctly, that Trump would win the election.

In April, looking ahead to the 2020 election, Abramowitz published a range of likely forecasts of the Electoral College vote using second-quarter economic growth and Trump’s overall approval (his negative rating subtracted from his positive rating) as his key variables. Under a significant slowdown, where the economy does not grow in the first half of next year, Trump loses even if he pulls the impossible (for him) and shrinks the gap between his approval and disapproval ratings. Under a modest slowdown, where the economy is growing at about 1 percent, he loses unless he eliminates that gap. But if the economy continues on its path — if there’s 2 percent or 3 percent growth in the first half of next year — then Abramowitz projects a Trump win even if his disapproval rating rises.

Donald Trump is a bizarre man to have as president. He confounds the conventional wisdom about politics. But he’s also been subject to the typical rules of politics. When he does unpopular things, he becomes unpopular. Political gravity exists, and it has kept him at a disadvantage.

But the problem with making predictions — or just trying to think through the next few years of American life — is that most unpopular presidents don’t have a strong economy behind them. Will voters remove the president they dislike, or reward him with a second term despite their personal misgivings?