Nothing is certain except for death and taxes. But in campaign season, it’s awfully predictable that Democratic politicians will do a little chest thumping about foreign policy. As the 2012 presidential contest approaches, the Obama administration is ratcheting up its rhetoric against Iran, right on cue.

First, the Justice Department lodged the allegation -- based on thin evidence -- that Iran’s Revolutionary Guards had plotted to assassinate the Saudi ambassador in Washington. “An outrageous act,” said Vice President Joe Biden.

Then, in November, the White House seized upon the latest report from the International Atomic Energy Agency (IAEA) to renew the US claim that Tehran is pursuing a nuclear weapon. “A very grave threat to all of us,” said Defense Secretary Leon Panetta. “We have not taken any options off the table.”

Some of this talk is pre-election theater. The Democratic Party has tried to out-hawk Republicans since the early days of the Cold War. And, since the 1979-1980 Iran hostage crisis, there has been nothing but upside to Tehran bashing for politicians of any party.

But there’s more at stake in the rattling of sabers at Iran than scoring political points. One worry is that the Obama administration will mire itself in its own bombast, pursuing aggressive policies against Iran simply to shore up US credibility. Democrats got us into Vietnam, and got nearly 60,000 Americans killed, for essentially this reason. But the more immediate concern is that Iran has volatile domestic politics, too.

Tehran’s hardliners hear Washington’s threats as proof that “the global arrogance” (their new term for the Great Satan) won’t rest until their regime is deposed, no matter what Iran does. They have jumped on the IAEA report to buttress their arguments. The report contains evidence that Iran looked at military applications of nuclear research up to 2003, but no proof of similar efforts since then, and certainly no indication that Iran has nuclear weapons capacity or could have it soon. Hence the hardliners denounce IAEA investigations as fig leaves for US belligerence and decry any Iranian politician who wants to talk with the West as naïve or worse. It doesn’t help that the West has long tried to deny Iran the right to nuclear research for peaceful purposes.

The result is diminished political space for reformers in Tehran and heightened tensions on the international stage.

The fact is that no one outside the Islamic Republic’s innermost circles, not the IAEA and not the White House, knows if Iran will get the bomb. The question is motivation, not capability, for ultimately the technical challenges can be surmounted. Given this reality, one would think Washington would want to reduce Iran’s incentives to look at warhead designs again. The Obama administration should quit hinting that airstrikes or other attacks are “on the table” and disavow any wish to overthrow the Islamic Republic. Like any other state, the Islamic Republic fears first and foremost for its survival. If external peril were gone, the hardliners would lose one of their handiest political tools.

But US conservatives -- and many Democrats -- insist on viewing Iran as incorrigible. To them, the IAEA’s finding that Iran stopped its study of military applications in 2003 is evidence not of flexibility, but of ill intent. They wind up promoting the same caricature of Iranians that the hardline ayatollahs preach about Americans.

For now, it looks like the Obama administration and its allies are content to impose tighter sanctions on Iran, keeping other “options” in reserve. But the trajectory of Washington’s Iran policy is reminiscent of how it dealt with Saddam’s Iraq in the decade before the 2003 invasion. There was a cycle of mutual suspicion that spun ever faster, in ever tighter circles, until it unleashed an unnecessary war.

The Obama administration must summon the courage to halt the downward spiral. That doesn’t mean appeasing Iran, as the Republicans will say, but acknowledging that Iran is a state like any other, with legitimate security concerns of its own.