A foolish consistency, Ralph Waldo Emerson once wrote, is “the hobgoblin of little minds.”

It’s also, as we see almost daily, the bane of presidential candidates, who often come under attack for inconsistency but rarely get the praise they deserve for revising ill-conceived positions.

And most do it. It’s a rare public official who, during their career, maintains the same positions on every issue. Indeed, most successful presidential candidates have revised some campaign positions when faced with the realities of office.

The elder George Bush sounded more hawkish than Ronald Reagan toward the Soviet Union during the 1988 campaign but forged a relationship with Mikhail Gorbachev that helped the longtime U.S. rival move toward democracy.

Bill Clinton campaigned on a middle-class tax cut before aides led by Treasury Secretary Lloyd Bentsen sold him the deficit reduction policy that helped produce a steady economic expansion.

And candidate George W. Bush criticized efforts to foster international “nation building,” only to embrace it as president by undertaking to bring democracy to Afghanistan and Iraq.

The shifts by the elder Bush and Clinton produced substantial benefits for the United States. And it’s hard to fault the current president’s goal, despite doubts about the prospects.

In this campaign, one of the main White House arguments is that John Kerry is advocating policies at odds with his record. Democrats make similar charges against Bush.

Kerry took a different position on Iraq in 2002 than a decade earlier. In 1991, he joined most Democrats in opposing authority to use force to make Saddam Hussein abandon his conquest of Kuwait. Given the U.S.-led success then, that vote looks like a mistake.

That may be one reason he voted to authorize President Bush to use force against Iraq, though his comments at the time displayed much of the same ambivalence he still shows sometimes in explaining his opposition to the way the president used the authority.

Kerry also voted to cut funds for various weapons systems and for intelligence. Now, he favors a bigger military and an intelligence overhaul. In both cases, he’s taken more popular and defensible positions.

He’s come under fire from the Bush campaign as a flip-flopper for making those changes. But on some other issues, it looks like the flip-flop belongs on Bush’s foot.

Just days after the White House reacted cautiously to the Sept. 11 commission’s recommendations for structural changes in the government’s intelligence agencies, he embraced proposals for a centralized intelligence director and a national counterterrorism center.

That was reminiscent of how, after months of opposing a new federal agency to coordinate homeland security, Bush proposed creation of a Cabinet-level Department of Homeland Security. Or how, after opposing an independent panel to investigate the Sept. 11 attacks, he reversed himself and supported a commission.

As with Kerry, these are cases where inconsistency produced the right decision — and made for good politics. In other areas, both men have run into trouble for sticking with positions.

The Massachusetts senator has looked awkward and unpersuasive in trying to defend his vote against an additional $87 billion for Iraq and Afghanistan.

Bush, meanwhile, persists in pushing for more tax cuts despite a deteriorating federal fiscal situation, refuses to admit any errors in Iraq and continues to flout close national and Senate divisions with his judicial nominations.

In all three cases, a little less consistency might have served the president and the country better, both politically and substantively.

Carl P. Leubsdorf is Washington bureau chief of The Dallas Morning News.