The moderate GOP counterrevolutionaries can always argue that their candidates are conservative enough. They can and often have argued that the conservatives they face off against are hypocrites. (In this Idaho race, they have attacked Smith for his trial lawyer career and his past opposition to tort reform in Idaho.) The Main Street defenders can also attack Tea Partiers as bloodthirsty purists conducting a damaging purge of the party.

Those arguments are all fair game, and at least worth examining in each case. But LaTourette and his allies have a much deeper problem — a problem that money can’t solve — if their strategy is to to disguise themselves as conservative purists, beset on all sides by crypto-Pelosi-lovers. Setting aside the dishonesty employed here to make the case, the Main Streeters cannot win by building up the very sensibilities that put their brand of Republicanism out of fashion in the first place.

The moderates’ message, wherever it has succeeded, is one of realism, pragmatism, “common sense.” In Idaho, LaTourette’s group has abandoned this for a straight-up appeal to paranoia about liberal Republican infiltrators — in this case, the “liberal” Club for Growth, which has been getting conservatives elected to office for a decade.

That approach could win the Main Street defenders an election here or there, but it certainly won’t convince anyone they have something of value to offer the party.