Conservative vs. conservative.

That’s the nature of a key Republican U.S. Senate primary race out west, in Arizona.

John McCain, the incumbent, is facing a challenge from former radio talk show host and ex-U.S. Rep. J.D. Hayworth, who says — get this — that McCain isn’t conservative enough.

Interesting stuff.

McCain, as many millions of Americans are aware, is a war hero. He was captured by North Vietnamese soldiers when his plane was shot down in 1967. This valiant naval aviator spent more than five years being tortured and beaten within an inch of his life in captivity. Yet he continued to resist his captors’ attempts to pry information from him. McCain rejected an offer for an early release from his prison cell in Hanoi.

And now he’s being challenged by an upstart who thinks McCain — who has had the temerity during his long congressional career to work Democrats — doesn’t quite fit the mold of an Arizona conservative.

Hayworth has hung that terrible “moderate” monicker on McCain.

Someone needs to remind Hayworth that McCain, the GOP nominee for president in 2008, was conservative enough for many middle Americans. McCain captured 80 percent of the vote in the Texas Panhandle, even though a good many Republicans here grumbled that McCain was just too darn moderate for their liking. Still, he polled tremendously in this part of the country.

McCain no doubt will pull out the heavy artillery to use against Hayworth.

What else would one expect from someone who’s taken part in an actual war, not just a mere political skirmish?