Despite the polling numbers, Americans are largely split over a U.S. military attack on Iran (support ranges from 41 to 56 percent) and there is broad approval for stronger economic sanctions and diplomatic action. Interestingly, the action favored by most Americans (81 percent), "direct diplomatic talks between the United States and Iran," is not part of the Obama administration's strategy.

In addition to the lukewarm support among Americans for attacking Iran, President Obama or his successor would also have to tackle two problematic assessments from the U.S Intelligence Community (IC).

First, as Director of National Intelligence James Clapper has repeatedly reaffirmed since late January, "we don't believe they've actually made the decision to go ahead with a nuclear weapon." Just yesterday, James Risen reported in the New York Times that the IC continues to believe (based on an assessment first made in November 2007) that Iranian Supreme Leader Ayatollah Ali Khamenei halted his country's nuclear weapons activities in 2003.

This might be hard for many to grasp, since polling has found the American people disagree with the collective judgment of the 210,000 civilian and military employees and 30,000 private contractors comprising the IC. A recent poll found that 84 percent of Americans think Iran is developing nuclear weapons, while another from February 2010 concluded that 71 percent of Americans believe that Iran currently has nuclear weapons.

Second, Lieutenant General Ronald Burgess, chief of the Defense Intelligence Agency (DIA) told the Senate Armed Services Committee in February that, despite all of Iran's threats, "it is unlikely to initiate or intentionally provoke a conflict or launch a preemptive attack." This assessment is undoubtedly difficult for some to reconcile with the rhetorical bluster of senior Iranian officials, including repeated threats to close the Strait of Hormuz if U.S. aircraft carriers entered the waterway.

In February, however, the USS Abraham Lincoln steamed through the strait without incident. In fact, Chief of Naval Operations Admiral Jonathan Greenert told reporters that Iran's naval forces have not responded with increased activity, adding: "The Iranian navy has been unto itself professional and courteous." This confirms what U.S. Navy officials have told me in private conversations: for the past two decades, the U.S. and Iranian navies have carefully avoided direct confrontations, and routinely cooperate on a tactical level to rescue distressed ships or lost seafarers.

To build up support for a preemptive attack, the U.S. president could play to the widely-held conviction that Tehran is nearing--or crossed--the nuclear threshold, but he will also need to explain why the intelligence professionals, on the receiving end of over $75 billion in taxpayer funds, are wrong.