In a famous 1979 television interview, Democratic presidential contender Ted Kennedy flubbed a softball question: "Why do you want to be president?" Mr. Kennedy's sputtering answer did real damage to his campaign. At the recent Saddleback Civil Forum on the Presidency, Senators Obama and McCain gave more coherent answers when Pastor Rick Warren asked the same question. But in an America with a saner perspective on the presidency, their answers would have been disqualifying as well.

What moved Barack Obama to seek the presidency was "the basic idea of empathy" and the notion that if "we see somebody down and out ... we care for them." Republican John McCain explained that he was running "to inspire a generation of Americans to serve a cause greater than their self-interest."

Noble sentiments, to be sure, but in the original constitutional scheme, the president was neither Empath-in-Chief nor a national life coach. His role was to faithfully execute the laws, defend the country from attack, and check Congress with the veto power whenever it exceeded its constitutional bounds.

What we expect the president to do

But there's a reason candidates talk the way they do. Their rhetoric faithfully reflects the public's outsized expectations for the office: Grow the economy. Give us better, cheaper healthcare. Protect us from hurricanes. Stop global warming. Bring peace to the Middle East. Lead us. Inspire us. We crave a spiritual superhero, not just someone who will "preserve, protect, and defend the Constitution."

As the conventions celebrate the anointed, it's worth exploring how our long slide away from the Founding Fathers' modest notion of presidential responsibility has left us with a dysfunctional politics and a bloated imperial presidency.

The McCain campaign has found its groove lately by skewering Mr. Obama's quasi-messianic pretensions. A recent McCain campaign ad, mockingly titled "The One," mixes clips of Obama speeches with Charlton Heston as Moses, parting the waters. "And the world shall receive [Obama's] blessings," the narrator intones. It's an effective ad, playing on the grating arrogance that periodically emerges from the Obama campaign. As Michele Obama said in February 2008: "Barack Obama is the only person in this race who understands that, that before we can work on the problems, we have to fix our souls. Our souls are broken in this nation."

But make no mistake: Both parties view the president as our national guardian and redeemer, a figure entrusted with the care of America's very soul.

It's a theme that President Bush has sounded repeatedly. And it's practically de rigueur for GOP presidential contenders. When Mike Huckabee announced his candidacy in January 2007, he said he was running because "America needs positive, optimistic leadership to kind of turn this country around, to see a revival of our national soul…."

Mr. McCain, too, sees the president as a soul-healer. His hero, Teddy Roosevelt, was a great president, McCain insists, because he "liberally interpreted the constitutional authority of the office," and "nourished the soul of a great nation."

If soul-nourishing is part of the president's job, what isn't?

That grandiose conception of the president's role couldn't be further from how our Founding Fathers saw the office. As The Federalist No. 69 tells us, the Constitution's chief executive officer had an important job, but he'd have "no particle of spiritual jurisdiction." Instead, as presidential scholar Jeffrey K. Tulis explains, unlike "polities that attempt to shape the souls of their citizenry and foster certain excellences or moral qualities by penetrating deeply into the 'private' sphere, the founders wanted their government to be limited to establishing and securing such a sphere."

The men who designed our Constitution never thought of the president as America's "national leader." Indeed, for them, the very notion of "national leadership" raised the possibility of authoritarian rule by a demagogue who would create an atmosphere of crisis in order to enhance his power.

Hard as it may be to imagine in the midst of a modern campaign season, the Framers wholly rejected the notion of the "bully pulpit."

Presidents were to be seen more than heard, which is why our first seven presidents averaged a little over three public speeches a year. Nor did early presidents follow the modern practice of referring to themselves as the "commander in chief," as if all America was a vast army directed by a supreme military leader. When George Washington referred to the office he held, most often it was with the humble term "chief magistrate."

Alas, humility is hard to discern on the modern campaign trail. If our presidential candidates seem to embrace an exalted notion of their status, perhaps that's a function of the adulation they're greeted with by the crowds at campaign appearances. A recent feature in The New York Times described the prevailing atmosphere: "Look at the faces – not of the candidates, but of the rope-liners themselves, with arms and fingers extended, their eyes bugged and sometimes tearful." "I got to smell him, and it was awesome," exclaimed Kate Homrich, who managed to get close to Obama at one campaign rally. Another, Bonnie Owens, got a finger-pinch from the Illinois senator: "Best experience of my life," she declared.

And it's not just voters at campaign rallies who fall prey to presidential idolatry. If anything, American political elites – pundits, talking heads, and presidential scholars – are worse. When President Bush traveled to Blacksburg, Va. to offer comfort after the April 2007 shooting rampage at Virginia Tech, David Gergen, adviser to one Democratic and three Republican presidents, commented, "At times like this, [the president] takes off his cap as commander in chief and puts on the robes of consoler in chief." Leon Panetta, former chief of staff to President Clinton, went even further: "In many ways, [the president] is our national chaplain."

Arthur Schlesinger Jr., author, ironically enough, of "The Imperial Presidency," captured the modern, bipartisan consensus in the introduction to his 1996 presidential ranking survey, maintaining that a great president needed to "have a deep connection with the needs, anxieties, dreams of the people."

Of course, the ability to channel the collective spirit of the American public isn't a skill that the chief magistrate needs to faithfully execute the laws or defend the country from foreign attacks. But that boundless view of presidential responsibility has helped lead to dramatically enhanced presidential power.

Some might counter, though, that all this "soul talk" is mere rhetoric. After all, it's not as though any president, concerned about spiritual "malaise," has appointed a "national-soul czar," charged with reforming the American spirit through the coercive power of government.

Terrible consequences

But ideas have consequences, and few ideas have had worse ones than the belief that Americans need grand federal crusades to pull them away from private, parochial concerns and invest their lives with meaning. As David Brooks wrote in a 1997 essay in The Weekly Standard, "…ultimately, American purpose can find its voice only in Washington…. Without vigorous national vision, we are plagued by anxiety and disquiet."

That helps explain why Washington doesn't just attempt to solve problems; it launches wars – on drugs, poverty, terror, disease. Noble aims all, but the destructive cost of these wars is mind-boggling. When he boosted drug war funding in December 2001, Bush declared that "when we fight against drugs, we fight for the souls of our fellow Americans." As a result of that fight, nearly half a million Americans are currently behind bars for drug offenses, and America has a per-capita prison population that dwarfs China's and Iran's.

The notion of president-as-spiritual-warrior has aided dangerous excesses in the war on terror. The week after 9/11, Bush announced that we would not only answer the attacks, we would also "rid the world of evil." A mission that vast demanded equally vast powers – powers that the public was all too willing to grant in the post-9-11 crisis atmosphere.

An increasing number of Americans worry that the presidency has grown too big, too powerful, and too menacing. Yet we also want the government – chiefly, the president – to "do more." And when terror strikes, hurricanes ravage, homes foreclose, the stock market drops, and food prices rise, we inevitably blame one person: the president.

Investing our lives with hope, uniting us all behind a higher calling, fixing our "broken" souls – none of this is remotely the president's business. It's not surprising that presidential contenders cater to our contradictory expectations. That's the business they're in. But if we're unhappy with the results, we ought to recall the wisdom contained in the Pogo Principle: "we have met the enemy and he is us."

So long as we embrace – or even tolerate – the idea that the president is the guardian of our national soul, we have little right to complain about our burgeoning Imperial Presidency.

• Gene Healy is a vice president at the Cato Institute and author of "The Cult of the Presidency: America's Dangerous Devotion to Executive Power."