Barack Obama is back to talking about negotiating with Iran. In Iowa today, he said a nuclear Iran would be a “game-changer for the region,” and that “no option is to be taken off the table, but in the meantime we have to make diplomatic progress.”

How about a game-changer for Obama? He used the same lines back in July, and they’ve grown no more substantive with age. If he is going to be champion of diplomacy until the eleventh hour, he needs to employ some of that famous out-of-the-box audacity and throw something–anything–specific and new into this long-failed calculus.

Obama has cast himself as George W. Bush’s (and John McCain’s) polar opposite here. Bush, according to Obama has been “saber-rattling” instead of employing effective diplomacy. This is a simple, digestible message of contrast that the Obama team has on an endless loop, but where is phase 2? How does Obama intend to use diplomacy effectively on a regime that’s been ignoring sanctions, threats, and incentives for decades? He’s had months and months to come up with something, and with only hours to go before the Democratic convention, here’s the best our visionary agent of change has to offer:

My job as president is to make sure we are tightening the screws on Iran diplomatically . . . to get sanctions in place so that Iran starts making a different calculation.

What screws? Sanctions are already supposedly in place. Tighten how? Europe has already demonstrated the extent of their willingness to pretend to exert pressure on Tehran. Does Obama plan to risk not healing all those supposedly nasty U.S.-EU rifts in order to–gasp–make Europe do more? And finally, just what does he think would make Iran calculate differently on the matter of nukes? If all the powers of the West could be brought to bear down on Iran, the mullahs would still go about ordering their scientists to spin centrifuges and erect missiles. Obama talks endlessly about games and tables as if Iran was a playroom instead of a potential theater of war. Diplomacy has failed with Iran because it is itself the wrong tool for the problem. If that’s not so, the Democratic nominee needs to tell Americans what could make it work.