CHARLOTTE, N.C. — When Ronald Reagan asked voters a week before the 1980 election whether they were better off than four years earlier, he turned a race that had been nip-and-tuck for months into a landslide victory — and showed how a pointed question can be a lethal political weapon.

Mitt Romney, the Republican presidential nominee, speaks often of that election in meetings with donors and other supporters, citing it to reassure those who are alarmed that he has not been able to build a lead against a president burdened with a listless economy, ballooning federal debt and a jobless rate deep in the red zone for an incumbent.

But if Mr. Romney believes the “Are you better off?” question will be political kryptonite for President Obama, he will have to reckon with an economic scorecard that is more mixed than he and other Republicans are claiming on the campaign trail. American voters, too, have more complicated feelings about their fortunes, and those of their children, than they did when Mr. Reagan first posed the question....