Here's one thing last week's congressional election wasn't about: foreign policy. The campaign was long, loud and polarized, but somehow the fact that the United States is at war in Afghanistan and Iraq — and carrying out bombings in Pakistan and Yemen — went almost unmentioned.

That's because voters were preoccupied by the economy, of course. But it's also because foreign policy has been a zone of relative bipartisanship in Washington, an oasis of civility compared with the battlegrounds of economic policy and healthcare.

That's about to end. As the 2012 presidential campaign gets underway, potential Republican candidates, including Sarah Palin and Mitt Romney, are sharpening their critiques of President Obama as a foreign policy leader. In Congress, meanwhile, the main victims of the election were middle-ground Democrats; the parties that remain are even more polarized between thoroughgoing liberals and hard-line conservatives.

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That leaves Obama in the middle, which could turn out to be a good spot. The president can't do much to make the economy recover more quickly, and he hasn't found a way to make his healthcare law more popular, but he still has the powers of his office in foreign policy. In diplomacy, unlike domestic policy, a president can act first and worry about Congress later.

The biggest issue, not surprisingly, will be Afghanistan, where Obama has more than doubled the number of U.S. troops but also set a target date of July 2011 to begin a gradual drawdown. Republican hawks such as Sen. John McCain (R-Ariz.) praised the escalation but criticized the exit date; Democratic doves such as Sen. Russell D. Feingold (D-Wis.), who lost his bid for reelection last week, weren't happy about the surge but took comfort in the calendar.

Obama has made it clear that he is serious about reducing the number of U.S. troops — and, even if that weren't his starting point, he faces pressure from within his own party to begin a drawdown soon. The most immediate danger to Obama's reelection would be a primary challenge from the left by Feingold or some other disenchanted dove, and the president would like to head that off. By comparison, criticism from the right could actually help him; the Afghan conflict is deeply unpopular, and Obama might benefit from casting his Republican opponents as champions of a bigger, longer, more expensive war.

Other foreign policy issues will test candidate Obama as well.

On Iran, the president kept a campaign promise to seek negotiations with Tehran over its nuclear program, which made hawks nervous; but so far, the main product of "engagement" has been stronger economic sanctions, which have quieted criticism from the right (except from a few super-hawks who favor preemptive U.S. military action). Now, Obama needs to catch a break on timing. Most estimates are that Iran is at least two years away from developing a nuclear weapon. If Iran buckles under economic sanctions and proposes a deal, Obama will face tough scrutiny from the right over the terms of any compromise, but that's a problem he'd be glad to face. In the unlikely event Iran succeeds in making a bomb before the election, that will become the greatest crisis of the Obama presidency, and his performance will define him in the eyes of voters.

In the Middle East, after initial missteps, Obama succeeded in relaunching peace negotiations between Israel and the Palestinians, but this is unlikely to hurt or help him much. His attempts to apply pressure to Israeli Prime Minister Benjamin Netanyahu have been lessons in the limits of U.S. power, not its possibilities. If Obama's popularity were still at its peak, he might be tempted to spend more time on Middle East peacemaking, but this is one case where political weakness at home makes activism abroad more hazardous. Americans don't always reward presidents who try to negotiate Israeli-Palestinian peace — think Jimmy Carter and George H.W. Bush. But that probably means Obama won't face recriminations if he fails either — unless voters feel that, in pursuing Middle East peace, the president ignored domestic crises.

Meanwhile, back in Washington, congressional Republicans will be doing everything they can to erode Obama's stature as a foreign policy leader well before the 2012 campaign.

Obama has asked the Senate to ratify the New START nuclear weapons reduction treaty with Russia in its lame-duck session this year. Republicans would rather defer the treaty to next year, when they will have more members in the Senate and more time to criticize Obama over the treaty's provisions.

The administration's hope of passing an energy bill that would include significant climate change measures — something Obama hoped to carry to his next international environmental summit — is dead.

And the administration's tentative steps toward opening more exchanges with Cuba will likely come to a halt before the determined opposition of the new chairman of the House Foreign Affairs Committee, Rep. Ileana Ros-Lehtinen (R-Fla.), a Cuban American conservative.

Still, foreign policy may be one area where Obama welcomes criticism from his opponents. Foreign policy made him his party's nominee in 2008, because of his opposition to the war in Iraq. His foreign policy since taking office has been relatively centrist — and reasonably successful too; he has scored no major triumphs but suffered no real disasters either.

Last week's election wasn't about foreign policy; if it had been, Democrats might have fared better. Obama has plenty of reasons to try to move foreign policy front and center the next time around.