Senator Hillary Clinton’s aura of inevitability has begun to wear off. After leading in national polls by 25 percent in the late summer and early fall, her poll numbers have begun to drop, and Senator Barack Obama’s have begun to increase.

Clinton’s decline is most readily apparent in Iowa — her leads in New Hampshire and South Carolina are still in the double digits. Polls in Iowa have shown her lead, which was once about seven points, now dwindling to nothing, as both Obama and Edwards pull into a statistical dead heat with her. Some polls have even show Obama in front. As the nation’s first state to vote (never mind absentee voters in Florida, California and elsewhere receiving their ballots a few days earlier), Iowa has considerable sway in shaping the rest of the campaign. It is true that some wackos — Pat Buchanan among them — have won Iowa in the past without going on to make waves in the rest of the campaign. But in this day and age, with a constant media news cycle, Iowans are now viewed as the kingmakers. The sight of presidential candidates from New York City pandering to Iowa farmers wanting to keep ethanol highly and outrageously subsidized is uniquely American and strangely important.

I rarely find myself agreeing with Karl Rove, but his recent statement that Obama needs to win Iowa to win the Democratic nomination is right. And an Iowa victory may be all he needs to defeat Clinton.

Here’s the logic: Clinton is the frontrunner nationally and in most states, despite her high negative ratings and concerns of electability. She will most likely be unable to shake that image heading into Iowa, her weakest state by far. But if Obama wins Iowa, even by just a single percentage point, he will monopolize media coverage of the results. And the media already loves Obama, despite his inability to gain any real ground on Clinton over a 10-month span and really command a knowledge of policy. Should he actually beat her, they’ll go crazy — as nuts as Ron Paul or Howard Dean after the 2004 caucuses.