It's not what he says, but how he says it.

The clip comes from NPR's interview with President Obama last Thursday. In it, Obama sums up what he considers his critics' argument — and laughs at it.

"So, the notion that somehow we are going to be safer by rejecting a deal that prevents Iran from getting a nuclear weapon and instead leaves Iran the option of installing more and more advanced centrifuges, shrinking their breakout time, that that somehow is going to make our neighbors more secure, I think, is kind of a — well, it doesn't make any sense," he says, laughing.

By the end of his remark, there is a long pause where it is possible to imagine the president pondering the use of a certain eight-letter word (known by the acronym B.S.) then thinking better of it.

The tone reflects the president's framing of his nuclear deal with Iran. He is treating his opponents with scorn.

His critics have focused on the perceived imperfections of the agreement: for example, that Iran agrees to limit its nuclear activity, but not forever. There's the fact that Iran may continue nuclear research, and that some Iranian sites are less immediately accessible to weapons inspectors than others. This is indeed a negotiated document that does not permanently remove the risk of a nuclear-armed Iran, something Obama acknowledged in our interview. The agreement's central purpose, as the president acknowledged in an earlier interview in April, is "purchasing" a period of relative nuclear security. Maybe Iran will change during that period. Or maybe not. Either way, he contends, the purchase is good.

Obama is challenging lawmakers and the public to compare it to the alternative: Do you want a potentiallyunfettered Iranian nuclear program sometime in the future, or a fairly unfettered Iranian program now?

To the president, the answer is obvious. Anyone who disagrees is either "illogical" or "ideological." (Never mind that the critics include some of his fellow Democrats, such as the party's Senate leader-in-waiting, Charles Schumer.) To the president, this agreement is not merely the best he could do, given the United States' legacy of conflict with Iran. Rather, it is "the strongest nonproliferation agreement ever negotiated," as he declared in a speech last week, going on to suggest that Americans who think otherwise resemble some of the more intransigent leaders of Iran.

To an extent, this approach reflects the box in which he has placed his critics. The deal is already made. Now it is being placed before Congress for a vote the president never thought he should have to face to begin with. Obama is arguing that if Congress rejects his choices, chaos or war will ensue. His opponents have been forced to come up with theories under which chaos would notensue.

His approach also reflects the cold political realities of the way the congressional vote has been set up. The vote as structured presumes that the president may do what he likes unless Congress affirmatively votes to block him. In other words, the president does not need a majority of lawmakers on his side. A minority of senators can filibuster any measure that rejects the deal. And if they should fail to stop it, Obama can veto the rejection and count on an even smaller minority of lawmakers to sustain him — just over one-third of either chamber would do.

For the president, then, there is no logic in a moderate course. He presumes he long ago lost most or all Republicans. He will also lose some Democrats. He needs to preserve a relatively small, hard core of support in order to survive yet another of the close calls that have marked his presidency. If the deal is passed, and succeeds, he predicts, "it'll probably be forgotten that Republicans uniformly opposed it."

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