SINCE MAY, the race for the 2008 Republican presidential nomination has been characterized by an unusual dynamic. At a time when national security issues are the foremost concern of GOP primary voters, a war hero with substantial experience defending the use of American power in Iraq and beyond has seen his support in national and state public opinion polls erode precipitously. That hero, Sen. John McCain of Arizona, saw his frontrunner status evaporate as two men who had not served in the U.S. armed forces–former New York City mayor Rudolph Giuliani and former Massachusetts governor Mitt Romney–dominated in fundraising and local and national public support. Many political analysts, reflecting widespread sentiment among Republican elites, saw McCain as irrelevant to the race and likely to withdraw.

Not anymore. Wednesday night’s Fox News Channel debate saw McCain reassert his place in the top tier of Republican contenders. And it was his answers on critical foreign policy questions involving Gen. David Petraeus’s “surge” strategy in Iraq, the interrogation techniques deployed on enemy detainees, and the use of military force against Iran that established his strong position. It increasingly seems clear that illegal immigration, the issue which dominated the Republican race throughout the spring and summer, and an issue on which McCain stands directly opposed to many in his party, will not be the issue on which the nomination is decided. To put it another way: Foreign policy has come home to roost.