Denouncing Republican "bluster" about war with Iran, President Obama went on the offensive Tuesday:

"Those who are ... beating the drums of war should explain clearly to the American people what they think the costs and benefits would be."

The president had in mind such remarks as those Newt Gingrich delivered to the Israeli lobby AIPAC that same day: "The red line is now ... because the Iranians are deepening their commitment to nuclear weapons" -- an assertion the Joint Chiefs and U.S. intelligence agencies say is blatantly false.

They insist: Iran has not made the decision to build a bomb.

Perhaps the president was referring to Mitt Romney's pledge to that same cheering throng to "station multiple carriers and warships at Iran's door" and deny Tehran even "the capacity to make a bomb."

But if "the capacity to make a bomb" means knowledge of how to build one and an ability to enrich uranium to bomb-grade, should they decide to do so, Iran already has that.

Does Mitt want war now?

Perhaps the president had in mind John McCain's call for U.S. air strikes on Syria, an act of war rejected even by GOP Speaker John Boehner as "premature," since the "situation in Syria is pretty complicated."

Have the Republican uber-hawks learned nothing from the war for which they beat the drums 10 years ago?

Then they told us Saddam Hussein was implicated in 9/11, that he had chemical weapons, that if we didn't invade his country we could expect anthrax attacks by Iraqi crop-dusters up and down our East Coast.

Those who asked for proof Saddam was a mortal threat were dismissed by Condi Rice: "There will always be some uncertainty about how quickly Saddam can acquire nuclear weapons. But we don't want the smoking gun to be a mushroom cloud."

The price of our heeding that bluster? Some 4,500 American dead, 35,000 wounded, $1 trillion sunk, 100,000 Iraqi dead, half a million widows and orphans.

The fruits of our victory? A Shia-dominated Iraq descending into sectarian and civil war.

The GOP's political reward for marching us up to Baghdad?

Loss of both houses of Congress in 2006 and the White House in 2008, when the antiwar Obama crushed the war hawk McCain.

Today's GOP front-runners -- Newt, Mitt and Rick Santorum -- all clearly believe that a warlike stance toward Iran will appeal to the evangelical base and to Jewish voters who went for Obama by 57 points in 2008.

But they are rolling the dice with a war-weary America.

Ron Paul, whose youth vote the party needs and who receives the largest number of contributions from the military, has split with them on Iran.

The president, says Paul, is "closer to my position than the other candidates, because what the other Republicans are saying is reckless."

Most Republicans seem to be lining up with Newt, Mitt and Rick on a more hawkish stance. Senate Minority Leader Mitch McConnell wants Congress to vote the president a blank check for war now. And the president is aware of and alarmed by the Republican stampede to war:

"The notion that the way to solve every one of these problems is to deploy our military -- that hasn't been true in the past and it won't be true now. ... Sometimes, it's necessary, but we don't do it casually. ... We think it through. We don't play politics with it."

When rash decisions are made about war, said the president, mistakes are made, and "typically it's not the folks who are popping off who pay the price."

What to do about Iran -- and whom to trust to deal with Iran -- seems fated to be the foreign policy issue of 2012.

And the battle lines are drawn.

Bibi Netanyahu, the Israeli lobby and its allies in Congress will be demanding ever harsher sanctions and military action before November. For they assume, rightly, that the president does not want war and, if he wins, there will be no war with Iran.

The Republicans will portray Obama as dithering, vacillating and weak, no true friend of Israel, though the U.S. military and intelligence community are behind Obama in his belief that a war now on Iran would be unnecessary, unwise and potentially calamitous.

Nervous Democrats, facing Sheldon Adelson super PAC ads in the Jewish communities of every swing state, all accusing Obama of "throwing Israel under the bus," will be pressuring the president to get tougher.

And Obama surely knows that an October confrontation with Iran, with war a possibility, or a reality, will mean the nation rallies around him and he wins a second term.

Will Iranian intransigence provide him a casus belli? Or will Iran negotiate seriously and agree to more intrusive inspections to prove its nuclear program is not aimed at a bomb?

Whether there is a U.S. war on Iran seems up to the ayatollah now. Will he play into the hands of Israeli and American hawks who are salivating over a war with his regime and his country?