Even before Barack Obama is sworn in as president, journalists and historians have begun the ritual of reevaluating his predecessors and deciding where George W. Bush fits into the pack.

The problem with most rankings is not that they’re subjective, but that they’re based on the wrong criteria, such as charisma, intellect, communications skill, leadership, or management style.

Some presidential scholars emphasize effectiveness or how a president responded to a crisis. Bland men in boring times rarely achieve much note.

It’s time to rethink the way we rate presidents. An effective president is not necessarily great, or even successful, if he effectively implements policies that are bad for the country.

Presidential rankings should be based on different standards: Did the president uphold the Constitution, and have an agenda that contributed to peace, prosperity, and liberty, and was he reasonably adept at getting that agenda implemented?

Presidents cannot take credit or be blamed for what they inherit when they take office. If they at least try to move the country in the right direction—as Jimmy Carter did when he proposed a top-to-bottom review of federal programs and government spending, known as “zero-based budgeting “—they deserve more credit than presidents who go along with things that are wrong.

Indeed, Carter, who is underrated as president, reduced government spending as a percentage of gross domestic product (GDP) faster than any other modern president, began deregulation of many industries, and nominated Paul Volcker to serve as Federal Reserve chairman. He was the main architect of the “tight money” policies that helped trigger the Reagan and Clinton booms.

The late historian Stephen Ambrose, biographer of Dwight D. Eisenhower, argued in his book “Eisenhower: Soldier and President,” that an author’s partisanship distorts the attempt to rate the effects of presidential decisions. A “more fruitful” way to judge a president, Mr. Ambrose wrote, is to assess “how well he did in achieving the tasks and goals he set for himself at the time he took office.”

Such valueless judgments are the opposite of how historians should judge our presidents. By Ambrose’s standard, any president with the skill—or the favorable conditions—to get his programs enacted could be labeled a good or great chief executive, even if the programs hurt the country. Woodrow Wilson, Lyndon Johnson and George W. Bush would all rank high in such a system, because they were all reasonably effective in getting (misguided) policies implemented.

But consider the cost of that effectiveness: Wilson’s policies arguably helped foment World War II, and they certainly led to bigger and more aggressive government. Johnson’s policies helped create welfare dependency as an American way of life. And Bush’s policies both dragged us into an unnecessary war in Iraq and, with the addition of Medicare’s prescription drug benefit, provided for the greatest expansion of government in recent history. All three were effective; all three were wrong.

Presidents also are frequently evaluated on how they respond to crises—rather than whether they could have prevented them. George Washington, Abraham Lincoln, and Franklin D. Roosevelt are consistently ranked among America’s greatest presidents. All three served during periods of great turmoil: the Revolution, the Civil War, and the Great Depression/World War II.

But why not give extra credit to presidents who keep us out of war? Ulysses S. Grant, for example, who kept us out of war with Spain in 1869–70 during a rebellion in Cuba, is generally rated lower in the history books than William McKinley, who took us to war against the same adversary for similar reasons in 1898.

Let’s be honest: Sometimes what a president doesn’t do is more important than what he does.

Martin Van Buren, for example, deserves high marks for acting with restraint during the economic panic of 1837, which prevented a deeper depression and allowed the market to correct itself. Compare that to the bail-everybody-out policies coming from Washington today.

He also avoided several wars, thus preserving limited government and restraining executive power. Compare that to the aggressive and activist policies coming from Washington today.

Calvin Coolidge lacked charisma, generally avoided government intervention, and served during a time of peace. He is known today as Silent Cal and is all but ignored by historians. I consider him among America’s best chief executives.

We need to judge our presidents not by who they were, how they led, or how they governed, but by what they did. If they upheld the Constitution and enhanced peace, prosperity, and liberty, they should be ranked high. If they detracted from these important qualities, they should be judged more harshly.