Whatever you think of Al Gore, it’s hard to deny the sheer strength of his current popularity. With an Oscar, an Emmy, and a Nobel Prize to his credit in 2007 alone, the former Vice President and current climate-change crusader seems perfectly positioned to win the highest office in the land.

Yet, despite a vigorous effort to draft him into the Presidential race, Gore insists that he’s “involved in a different kind of campaign.” There’s no doubt that Gore’s reluctance to run is genuine, but the fact that someone so passionately committed to global change has little interest in a presidential bid is a bad sign for the health of our political system.

Gore is not the only prominent leader to forgo the presidency in recent decades. Twenty years ago, pundits jokingly referred to the weak Democratic presidential field as the “seven dwarfs” after several well-respected Democrats refused to run. In 1996, Gulf War General Colin Powell rejected an independent presidential bid despite polls showing him besting both major-party nominees. And this year alone, a stunning array of popular politicians — from Secretary of State Condoleezza Rice to former House Speaker Newt Gingrich to former NATO General Wesley Clark — have rebuffed repeated efforts to draft them into the 2008 race.

It wasn’t always this hard to persuade great leaders to run for president. In the Federalist Papers, James Madison confidently predicted that the United States would “obtain for rulers, men who possess most wisdom to discern, and most virtue to pursue the common good of the society.”

His fellow Founding Fathers practically fell over themselves to prove Madison right; in the nation’s early years, every major statesman wanted to be president, even those clearly ill-suited for the job. John Quincy Adams, for example, an ornery career diplomat, was a far better secretary of state than candidate for elective office — but that didn’t stop him from running for, and winning, a single presidential term in 1824. When three-time loser Henry Clay declared that he’d “rather be right than President,” his statement reflected disappointment rather than a lack of ambition.

In the decades thereafter, a few leaders resisted the pull of the presidency. Civil War General William Tecumseh Sherman stunned Republicans in 1884 when he assured them that “if drafted, I will not run. If nominated, I will not accept. If elected, I will not serve.”

But most politicians were only too happy to seek the White House. Theodore Roosevelt, for instance, wanted to be president so much that he ran for a third term against his own hand-picked successor, William Howard Taft. In 1910, Roosevelt explained that he cared little for “those cold and timid souls” who shy away from political combat. “The credit,” he declared,” belongs to the man who is actually in the arena.”

Today, few leaders heed Roosevelt’s advice. Our men and women Òin the arena” seem more interested in running for the sidelines or, like Gore, in waging “a different kind of campaign.” Roosevelt would wonder what kind of campaign could possibly be more important than a presidential one. In one sense, he’d be right: the amount of good Gore could do as a climate change activist would be dwarfed by what he could accomplish for the environment as President.

But leaders like Gore seek more than just political power; they covet even more what Roosevelt called the “bully pulpit” of the presidency — the power to inspire and persuade, to change Americans’ minds on issues of national import. Thanks to increasing voter apathy, this function of presidential leadership seems headed for extinction.

A poll last year showed that more than a third of Americans thought voting on the TV show “American Idol” was more important than voting for president, and, in fact, the winning “Idol” that year received more votes than George Bush did in 2004. The uncomfortable truth is that many Americans are more interested in what’s sung on television than what’s said in the White House; consequently, men and women with something worth saying are less likely than ever before to seek to occupy the Oval Office.

A century ago, leaders with passion and vision lined up eagerly for presidential runs because they knew that a victory would secure for them the rapt attention of the nation and, with it, the ability to change the United States for the better. Today, Al Gore realizes that if he wants “to change the way people think” about our global climate, he needs to look outside political office.

It’s no wonder people have been disappointed in American political leaders for a generation. We can’t expect our most visionary leaders to take to the presidential pulpit when no one’s sitting in the pews.