But these kinds of nuanced arguments are usually not the stuff of campaign rallies. And if the overall economic numbers remain strong, the Democratic nominee will be looking for a pathway to defeat Mr. Trump that is distinctly different from those taken the last two times an incumbent president lost. Historically, when a president seeks re-election, it amounts to a referendum on the state of the economy.

The last two one-term presidents were undone by economic slowdowns; they battled jobless rates of 7.4 percent (George H.W. Bush) and 7.5 percent (Jimmy Carter) on Election Day. The unemployment rate currently stands at 3.6 percent.

Image Michael Bennet at an event in Washington. Credit... Yuri Gripas/Reuters

Moreover, voters appear to be more positive about the economy than they have been in many years. In polling by Gallup this spring, the share of Americans who described the economy as “excellent” hovered near its highest levels since 2000, and only 13 percent of Americans mentioned economic issues as the nation’s most important problem.

That helps explain why the candidates are avoiding frontal assaults on the economy. Most prefer to change the subject to longer-term problems than to get wrapped up in debates over the Obama economic record or budget deficits.

“The challenge that Trump could run into in 2020 is that people don’t measure the quality of their economic life in the jobs numbers they see,” said Jacob Leibenluft, who worked in the Obama White House and was a senior policy adviser on Hillary Clinton’s 2016 campaign. “If you look at what Trump has done from a policy perspective, there’s very little to suggest that he’s addressed the acute problems that people feel in their economic lives.”

Indeed, Democratic base voters — like those who showed up at campaign events recently in New Hampshire — tend to latch onto problems deeper than what macroeconomists normally talk about when evaluating the economy.