Rick Santorum doesn't fit any of the stereotypes of current foreign-policy ideologies. He's too idealistic to be a "realist," too conservative and too religious to be a "neocon," and too revolutionary to be a "paleocon." He's an old-fashioned, feisty patriot, in the mold of Harry Truman and Ronald Reagan.

Mr. Santorum believes the United States must lead the struggle for freedom throughout the world, on grounds of morality and national security, which he believes go hand in hand. He does not like the drift away from leadership and engagement in that struggle, especially under President Obama. He often quotes Lech Walesa's recent lament: "The United States was always the last resort and hope for all other nations," Poland's first post-communist president said. "There was the hope, whenever something was going wrong, one could count on the United States. Today, we have lost that hope."

Mr. Santorum wants to restore the hope that America will rescue those for whom things have gone terribly wrong. In Congress, he supported aid programs to help Africans suffering from AIDS and other terrible diseases (laying the foundation for his friendship with U2 singer Bono). He also has sponsored legislation to support democratic opponents of the Syrian and Iranian tyrannies—because their leaders, the Assad dynasty in Syria and Iran's Ali Khamenei and Mahmoud Ahmadinejad, threaten American and Israeli security, and because he wants to support moderate Muslims living under such regimes.

After leaving the Senate in 2007, Mr. Santorum wrote about foreign policy frequently for the Ethics and Public Policy Center, where he was a fellow until June of 2011. In essays written for the center, he acknowledges that terrorists are indeed inspired by radical Islam—but he wants to work with Muslims who do not wage jihad, subjugate women or oppress minorities. He's specific about the radicals: They are evil men who have perverted the meaning of "martyrdom," changing it from the act of dying for one's faith to killing others to advance the dominion of one's faith.