Bernd Debusmann is a Reuters columnist. The opinions expressed are his own.

After years of portraying Iran’s leaders as irrational actors driven by religious zeal, American neo-conservatives and their Israeli allies appear to be shelving the “mad mullah” argument used to underline the danger of Iran getting nuclear weapons. The mullahs are now seen as shrewd calculators of risk.

The change of tone was reflected in a report on Iran and the bomb by the American Enterprise Institute (AEI), the Washington-based conservative think tank whose hawkish views influenced the decision-making on going to war in Iraq.

The report, published this week, is based on the assumption that sanctions and sabotage will fail and Iran will have a nuclear weapon by the time the next U.S. president takes office in 2013.

And how, according to AEI, has Iran behaved on the road to the nuclear club? “There is a clear pattern … Far from being hothead provocateurs, Iran’s leaders – including both Supreme Leader (Ali) Khamenei and President (Mahmoud) Ahmadinejad – often play a shrewd, long game … The nuclear program is a case in point. Each escalation – conversion, enrichment, installation of advanced centrifuges, higher enrichment – has been dribbled out.”

“Iranian leaders have rarely been willing to provoke a crisis merely to shift the ground inexorably toward a particular goal. Nor is this an aberration. Historically, the Islamic Republic has handled trouble well and it has often emerged with its goals achieved at the end of each crisis.” In a passage on Afghanistan, the study notes that “Iran has pursued a pragmatic, cautious policy to exert influence.”