Here is a 2008 exchange between Candidate Barack Obama (D) and the Boston Globe concerning the US’ use of force against Iran’s nuclear facilities [emphasis added]:
Globe: In what circumstances, if any, would the president have constitutional authority to bomb Iran without seeking a use-of-force authorization from Congress? (Specifically, what about the strategic bombing of suspected nuclear sites—a situation that does not involve stopping an IMMINENT threat?)
Obama: The President does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.
As for the specific question about bombing suspected nuclear sites, I recently introduced SJ Res 23, which states in part that “any offensive military action taken by the United States against Iran must be explicitly authorized by Congress.”
In the Senate Foreign Relations Committee hearing earlier this week concerning US intervention in Syria, Senator Rand Paul (R, KY) offered this amendment to the draft authorization bill being debated:
It is the sense of the Senate that the President does not have the power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.
Paul’s amendment was voted down 14-4, with all 10 Democrats present voting against.
Apparently, the President does have that power, so long as he’s from the politically correct party.