What to make of this leak from "a senior administration official" to the NYT about a U.S.-Iran agreement to negotiate over nuclear power?

Quite aside from whether there really is such an agreement, why would the administration want to leak the news? There is also an official denial of the agreement, but that just means the administration wants it both ways, and the question remains: Why do they want this?

News of the agreement — a result of intense, secret exchanges between American and Iranian officials that date almost to the beginning of President Obama’s term — comes at a critical moment in the presidential contest, just two weeks before Election Day and the weekend before the final debate, which is to focus on national security and foreign policy.

It has the potential to help Mr. Obama make the case that he is nearing a diplomatic breakthrough in the decade-long effort by the world’s major powers to curb Tehran’s nuclear ambitions, but it could pose a risk if Iran is seen as using the prospect of the direct talks to buy time.

Is it a feint? How is Romney supposed to respond? The Obama team may have figured out the set of possible Romney responses and have Obama prepared to deliver a devastating response to whatever Romney chooses to do.