WASHINGTON — Rick Perry’s rapid lead over previous Republican front-runner Mitt Romney was predictable. But it is not a good sign for Republicans hoping to reclaim the White House and further highlights the crucial battle within GOP circles: Who is the godliest of us all?

That’s the mirror-mirror question for Republicans. Forget charisma, charm, intelligence, knowledge and that nuisance, “foreign-policy experience.” The race of the moment concerns which candidate is the truest believer.

This was always a tough hurdle for Romney, whose Mormonism is reflexively distrusted by Southern evangelicals. Even so, in the absence of a better candidate, Romney had a fighting chance to win his party’s support. Then came Perry.

Talk about a perfect-storm, composite candidate. Combine Elmer Gantry’s nose for converts, Ronald Reagan’s folksy confidence and Sarah Palin’s disdain for the elites — and that dog hunts.

Perry doesn’t just believe, he evangelizes. He summons prayer meetings. He reads scripture while callers are on hold. Not incidentally, he’s a successful governor. Perhaps most important, he’s a wall-scaling fundraiser whose instincts make him a force of nature in the political landscape.

If you’re Romney, Perry is a nightmare that’s still there in the morning. If you’re Barack Obama, maybe not so much?

Perry’s political instincts were in evidence when he timed his entrance into the race just as everybody else was trying to grab straws in the Iowa poll. If life is high school in adult relief, Perry is the guy who shows up in a truck with a winch and pulls the car out of the ditch while those other guys are looking for a jack.

Whether you like his politics or not, he emits a pheromonal can-do-ness. Apparently, plenty of Republicans do like his politics, which has much to do with the very devil-may-care attitude that eventually will become Perry’s cross to bear. Gallup’s recent polling shows him not just passing Romney, but dusting him. Among Republican voters, 29 percent now swear their allegiance to the Texas governor compared to just 17 percent for Romney.

Huddled around the exhaust pipe are, you got it, the jack handlers: Ron Paul (13 percent) and Michele Bachmann (10 percent), followed by Herman Cain, Newt Gingrich, Rick Santorum and Jon Huntsman in the single digits.

Perry’s campaign strategy is to talk only about jobs, jobs, jobs, no matter what the question. That’s both smart and necessary, but jobs-jobs-jobs isn’t the money trinity with his base. Perry already hit that station with his prayer rally and various dog whistles to the congregation: He’s not sure anyone knows how old Earth is, evolution is just a “theory,” and global warming isn’t man-made.

That we are yet again debating evolutionary theory and Earth’s origins — and that candidates now have to declare where they stand on established science — should be a signal that we are slip-sliding toward governance by emotion rather than reason. But it’s important to understand what’s undergirding the debate. It has little to do with a given candidate’s policy and everything to do with whether he or she believes in God.

If we are descended of some blend of apes, then we can’t have been created in God’s image. If we establish Earth’s age at 4.5 billion years, then we contradict the biblical view that God created the world just 6,500 years ago. And finally, if we say that climate change is partly the result of man’s actions, then God can’t be the One who punishes man’s sins with floods, droughts, earthquakes and hurricanes. If He wants the climate to change, then He will so ordain and we’ll pray more.

Perry knows he has to make clear that God is his wingman. And this conviction seems not only to be sincere, but also to be relatively noncontroversial in the GOP’s church — and perhaps beyond. He understands that his base cares more that the president is clear on his ranking in the planetary order than whether he can schmooze with European leaders or, heaven forbid, the media. And this is why Perry could easily steal the nomination from Romney.

And also why he probably can’t win a national election, in which large swaths of the electorate would prefer that their president keep his religion close and be respectful of knowledge that has evolved from thousands of years of human struggle against superstition and the kind of literal-mindedness that leads straight to the dark ages.

Faith and reason are not mutually exclusive, but Perry makes you think they are.