America has generally been lucky in its selection of presidents. Not that we haven't had our share of shitty ones (thanks for the 30 days, Harrison), but we've produced some of our finest leaders when we truly needed them.

Which one would you want leading your country?

In fact, the shitty ones usually proceeded the great ones. Several of the darkest times in American history were precipitated by extremely bad presidents. Although some sort of confrontation between the North and South was probably inevitable, the slave states' succession was virtually guaranteed by the successively sucky presidencies of Franklin Pierce and James Buchanan. If Buchanan had been president for another four years, the Southern states might very well have just waltzed out of the Union.

Instead, we got Abraham Lincoln — maybe the perfect man for that time and place, and probably our greatest president. Some argue that men are called to greatness by great challenges, that many other presidents could have done as well as Lincoln in his place. Buchanan and Pierce say otherwise. As does the man who followed Lincoln: Andrew Johnson, another of our worst presidents.

The Great Depression was as great a crisis as the Civil War. And like the Civil War, it was worsened by the ineffective leadership of Herbert Hoover. Had Franklin Delano Roosevelt not followed Hoover in the White House, our entire system of government might have fallen apart. At a time when we needed perseverance, courage and vision, FDR provided those in spades. Like Lincoln, he was the man we needed to lead the United States through both the Depression and the Second World War.

It feels like we're at another one of those points. The threats to America aren't as simply labeled as "civil war" or "economic collapse" this time. We're facing a rising tide of anti-Americanism in the world, spearheaded by a religious movement that would like nothing better than to send civilization back to the 10th Century. Russia is making a sideways dash back at dictatorship. China and India are revving up for a run at American economic hegemony. Global warming may be on its way to a global catastrophe, and we're making it worse as we continue to guzzle a vanishing resource which is, what do you know, controlled by those aforementioned religious crazies.

And like previous dark days, we are stuck with a government which is simply not up to the challenge. The Bush administration and its Republican-controlled Congress are fundamentally unserious about governing at a time when we face threats that may be more dire than any of the past few generations. For all his talk about the dangers of Islamic terrorism, Bush has done precious little to attack the problem at its roots.

A first step is for the opposition party to retake one or more houses of Congress in November. But the Democrats will spend most of the next few years simply trying to check Bush's power grabs and undo some of his worst excesses. While they wrangle, Rome burns.

To succeed in the coming years, America needs someone who will honestly talk to the nation about the threats we face and ask us to sacrifice to surmount those threats. That kind of transformative leadership must always come from the presidency. What will we do if we get the kind sort of business-as-usual president we've had for most of U.S. history? What if democracy fails to cough up the leader we need?

It's impossible to know where that leadership might come from, but the names being floated for 2008 don't inspire a lot of confidence. Hillary Clinton. Rudi Giuliani. George Allen. John Kerry. Newt Gingrich. Jeb freaking Bush.

A few others might be better. John McCain, if he can truly be the truth-telling rebel he claims to be, rather than just a Republican who likes to feud with his party occasionally. Al Gore has certainly shown us something over the last several months.

But I'm holding out hope for something better. So far, it has been the genius of our system to provide us with just the leader we need just when we need him. So let's keep our eyes open. After all, our greatest president was a relative newcomer to the national political scene who made his name in Illinois politics and gained fame on the strength of his great oration. You never know where one of those might turn up again.