The other theory to explain Obama’s perilous slide in the polls is simply that the economy is still bad and unemployment is worsening. Certainly much of Obama’s slide in the polls followed the release of the July unemployment figures. As talk turned to the prospect of double-digit unemployment and the failed stimulus plan, his poll numbers floated downward. If you buy that people are just grumpy about unemployment, then Obama need not change the trajectory of his presidency. He might be blamed in the short run for overpromising on those 3.5-4 million jobs he was going to “save or create,” but as unemployment eventually subsides his approval numbers will go up.

Still, this won’t entirely please House Democrats and those senators on the ballot in 2010. They have to face re-election in a time frame which likely will precede a dramatic reduction in unemployment. If the current poll numbers are based on “where are the jobs?” then 2010 becomes a jobs election and incumbents should be very afraid.

Whichever theory you favor, the result may be the same. The president’s poll numbers for awhile will drift downward. Wary congressional Democrats ( who now trail the much-maligned “Party of No” in some generic polling) will seek to put distance between themselves and the politically ailing president. And the media — deprived of a credible storyline that Obama is simply the most popular, perfect president ever — will perhaps stiffen its collective spine. In short, this is the beginning, not the end of Obama’s political travails.

Every president faces a rough patch or two, but Obama’s may be a bit more troubling than most. A presidency that rests on a cult of personality rather than the power of ideas is particularly vulnerable when the personality proves to be less attractive.

Moreover, Obama has not expended political capital on anything meaningful. He did not, as Ronald Reagan did, suffer a drop in the polls by doing the hard work of wringing inflation from the economy. He didn’t enrage liberals by refusing to retreat from an unpopular war or  risk the ire of the conservative base to pass a largely successful Medicare Part D, as did George W. Bush. Obama lost his popularity with only a failed stimulus plan to show for it. He has not worked to sow the seeds of policy initiatives which will bear fruit later on. He has frittered away his high standing on government boondoggles.

It would be a mistake to conclude Obama is permanently hobbled. His large congressional majorities may well deliver some type of health care reform for which he can claim credit. And the economy will eventually rebound. But what has been lost is that “opportunity” which Rahm Emanuel bragged about to use both the recession and Obama’s personal popularity to enact a fundamental shift in our government.

Whether due to political overreach or to sagging employment, the chance to remake America to suit Obama’s liberal vision is quickly slipping from the president’s grasp. And you don’t get opportunities like that very often.