No single cause explains all of these results, positive and negative, for the president’s party. But from these cases, the clearest rule might be that midterm elections turn less on assessments of legislation that may eventually affect people’s lives than on verdicts about the country’s condition in the here and now. Medicare and Medicaid didn’t cause the Democratic losses in 1966, but they weren’t enough to overcome discontent over inflation, urban turmoil after the Watts Riots of 1965, and Vietnam. Reagan’s tax cuts didn’t trigger the GOP losses in 1982, but they weren’t enough to overcome discontent over high interest rates and double-digit unemployment. An old political adage holds that presidential elections are always about the future; midterms seem to be more about today. As Bolger put it to me, voters “step outside and feel how the weather is, and if I feel uncomfortable with it, I take it out on the incumbent party.”

Maybe the most remarkable proof that current conditions outweigh legislative achievements in midterm elections is a data point that the Emory University political scientist Alan Abramowitz calculated for me from the University of Michigan’s National Election Studies covering the 1964 and 1966 elections. According to Abramowitz’s analysis of the results, those surveys found that even after Democrats created Medicare, the party’s share of the vote among seniors in House elections fell slightly from 1964 to ’66, giving the GOP a slight majority among them…

However popular individual elements of the Democratic plan might be, Zelizer says, the 1966 precedent offers a blueprint for how Republicans can neutralize them, at least while voters have not yet fully felt their effects. The attack message back then, he says, “wasn’t specific to the programs. It was about ‘Skyrocketing prices are on the way; spending is out of control,’ and that is the trap Biden is potentially falling into.” (A political action committee associated with Senate Minority Leader Mitch McConnell is already launching ads targeting the cumulative cost of the Democratic program.)