Over the past weeks much has been made of Barack Obama's hard right turn toward the center of the political spectrum. There's been no greater about-face than his embrace of the Bush Doctrine on the next likely foreign policy crisis - Iran.

The Bush Doctrine refers to the strategy of preemptive warfare that President Bush set forth in 2002. It's the idea that the United States will not wait for menacing enemies to attack us; we will attack preemptively in certain cases.

But how, you might ask, can the candidate of MoveOn.org and the antiwar-forever crowd be aligned with Bush on preemptive strikes against Iran? Here's how: Last month, Obama declared, "I will do everything in my power to prevent Iran from obtaining a nuclear weapon, everything in my power to prevent Iran from obtaining a nuclear weapon - everything."

When a would-be commander in chief says "everything" three times in one sentence - and says so publicly - he is not just talking about continued diplomacy and sanctions. He's saying that he has not taken the military option off the table.

With that statement, Obama, the definitive antiwar candidate, ended any serious debate over preemption in the post-9/11 world.

And none too soon.

International Atomic Energy Administration director Mohamed ElBaradei said last month that if Iran expelled the United Nations' nuclear watchdog agency, Iran would need six months to produce a nuclear weapon. Couple that with last week's test firing of missiles capable of delivering that weapon to Israel, and it is no wonder you have seen a rash of stories about the Israelis training for strikes against Iran.

Everyone hopes, of course, that the United States and the West might persuade Iran to give up its nuclear ambitions with measures short of military action. But things aren't looking too promising.

Either way, the fundamental issue remains: Preemption or containment - is a nuclear-armed Iran acceptable if economic sanctions and diplomatic pressures fail?

Obama's primary-season supporters would argue that a pre-emptive strike poses far greater danger than a nuclear Iran. Iran, the argument runs, can be "kept in a box," as happened with the Soviet Union during the Cold War.

Here are a few problems with that argument:

Iran's ruling mullahs and their bombastic, hand-picked president, Mahmoud Ahmadinejad, are not the Politburo and Nikita Khrushchev. For starters, Soviet leaders had absolute control over their weapons and launch codes. Given the leadership struggle among Iran's military, mullahs and political leadership, control of that nation's nuclear arms would be subject to ongoing internal power plays. This would increase the chance of an "unplanned" launch as well as a weapon falling into the hands of Islamic terrorists.

We trusted the Soviets to act rationally and respond rationally to our actions. History proved we were right to do so. Given the radical nature of the Ahmadinejad's regime, his promise to "wipe Israel off the map" and his nation's close theological and military ties to terrorist organizations, we cannot expect the same from the Iranians.

Today's nuclear chess game would have three or more nuclear powers, not just two, playing at the same time and exponentially increasing complexity and uncertainty. On top of that the game is being played in a region where brinkmanship and deception are standard operating procedures.

Most important, Soviet leaders were avowed atheists; all that mattered to them was this life. Death and annihilation were not attractive options. Thus, the Mutual Assured Destruction (MAD) doctrine made sense. Iran's leaders believe all that matters is the next life. Killing, or being killed by, infidels in defense of Islam is the surest way to get you there with a posse of virgins at your disposal.

Thankfully, Bush, Obama and John McCain have all promised to use every means necessary to keep Iran from acquiring nuclear weapons. But if we fail to deliver on this promise, what Middle East ally would then trust us to protect them? The result - more nuclear nations.

And if you think oil prices are high today, think about the power that a nuclear Iran would have to use oil as a weapon to drive the price to $250 a barrel or more.

I have heard from many sources that our allies, including our Arab allies, ask us one question and one question only today: When are we going to give Israel the green light?

Given McCain and Obama's comments to date, it appears that when that moment comes - and come I fear it will - both presidential nominees will stand behind President Bush and our allies.

Or will they?

E-mail Rick Santorum at rsantorum@phillynews.com.