With John McCain now clearly headed for the Republican presidential nomination, attention is turning to who he will choose as a running mate.

One early favorite is former Arkansas Gov. Mike Huckabee, the darling of the evangelicals. But if Mr. McCain is the man he and his supporters say he is, he won’t do that to the country.

Perhaps no decision Mr. McCain makes will be more important than his choice of a vice president.

Mr. McCain will be 72 years old if he is inaugurated a year from now, making him the oldest man ever to enter the White House. He likes to talk about his 95-year-old mother to illustrate his good genes, but the presidency is a very stressful job. There are indeed terrorists out to get the American president, five-and-a-half years in a North Vietnamese prison can’t be good for your health, and he has had a bout with skin cancer. Furthermore, his mother’s age notwithstanding, his father died at 70 and his grandfather at 61. So he has to recognize at least the possibility that he might not serve out his term. At a time of international turmoil, it is essential that a president, especially one so committed to duty, honor and country, leave the country in capable hands in that eventuality.

Could Mr. McCain honorably serve his country by putting Mike Huckabee a heartbeat from the presidency? There’s some political plausibility. Mr. Huckabee is younger. He would reassure religious conservatives who might be skeptical of Mr. McCain. He’s a charming and effective campaigner. On the other hand, his political appeal largely has been limited to southern evangelicals, who are surely going to vote for any Republican candidate in November.

But from a policy perspective, he’s a big-spending nanny statist. He bills himself as a “Christian leader” and says that his rise in the polls can only be attributed to God’s will.

Mr. Huckabee doesn’t just want a government that will stamp out sin. He wants a government that will worry about your body as much as your soul. He says that “it is government’s responsibility to try to create a culture of health,” including pressuring employers to “encourage” healthier lifestyles among their employees. He wants a federal ban on smoking in the workplace and other public places. He’s even threatened to ban cigarettes altogether. He wants federal regulation of local schools and restaurant menus.

But more importantly for Mr. McCain, Mr. Huckabee has no experience and apparently no knowledge of foreign policy. When the journal Foreign Affairs inexplicably asked him for an essay, he wrote about the “Bush administration’s arrogant bunker mentality” — and then, when his remarks were reported, he ran away from them. He demonstrated minimal knowledge about Pakistan in his remarks on Benazir Bhutto’s assassination.

He offers veiled protectionist rhetoric like “We can’t have free trade if it’s not fair trade.” When asked about the blockbuster National Intelligence Estimate on Iran’s nuclear capability, he said that “nobody’s going to be able, if they’ve been campaigning as hard as we have been, to keep up with every single thing, from what happened to Britney last night to who won Dancing with the Stars.”

To be sure, neither Bill Clinton nor George W. Bush had much foreign policy experience as governor either (and we’ve seen how well that worked out), but Huckabee seems to have far less background even than they did.

It’s hard to imagine that a man who values duty, honor, and country would put a self-styled “Christian leader” who doesn’t read the newspaper a heartbeat from the presidency.