In the 1950s, Dwight Eisenhower was considered a responsible steward of an economy that was poised to convert wartime productivity into peacetime bounty. During World War II American factories had learned productivity lessons that they later applied to making cars and refrigerators. The economy benefited from the mass adoption of several technologies, such as television and air conditioning, which had been invented decades prior but had not caught on because of the war and Depression. With much of the world still coping with the aftermath of war, the U.S. was the world's factory, and wages for middle-class workers soared. (To be fair, Dwight Eisenhower was not an entirely passive observer of the economy; he built a 40,000-mile Interstate Highway System, with debatable benefits, and expanded Social Security, but the economy would have been sterling without these measures.)

Hillary Clinton offers up the ‘90s as evidence of her husband’s economic savvy. But he, too, was a beneficiary of historic good fortune. Clinton passed some policies that helped the economy flourish, but the middle class was bound to flourish right then thanks to “the rise of the internet and the entrance of the baby boomers into their peak earning years,” as Ben Casselman wrote in FiveThirtyEight. (Moreover, just as later generations criticized the ​effects of Eisenhower’s ​Interstate highway project, many would argue that Clinton’s welfare reform and financial deregulation also had extremely negative consequences.)

Ronald Reagan savior act is so widely worshipped that people call the 1980s “the Reagan Recovery.” But the Gipper also occupied the Oval Office at an auspicious time. Today, even some Reagan supporters acknowledge that the most important contributor to 1980s recovery wasn’t his vaunted tax cuts or stimulating defense spending. Paul Volcker, the chairman of the Federal Reserve, had triggered the recession with restrictive monetary policy in the early 1980s to tame inflation. When inflation has sufficiently dropped, he loosened monetary policy, and the economy sprung back to life.

At extremes, presidents have hurt the economy or, with the help of Congress, rescued it from catastrophe. But these are extraordinary cases, and they’ve typically required extraordinary help from Congress. Most recently, the 2009 stimulus act—the largest such measure in American history—increased short-term growth and blunted the Great Recession. But Congress obstructed his later efforts to expand the stimulus, another reminder of the presidency’s limits. The U.S. government is like an ocean liner and the presidency a small rudder; by design, it is difficult to turn dramatically, and impossible to turn quickly.

If it doesn’t make sense to see presidents as heroic saviors of the economy, then what’s the right way to see their contribution to the economy?