Click here to watch "Consistent Conservative."

After both faced negative advertising from a third-party group, the two Republican members of Congress vying to replace Sen. Pete Domenici (R) have each released negative ads of their own -- against each other.

Two weeks ago, Rep. Steve Pearce released a TV ad, "Consistent Conservative," claiming the conservative mantle for himself and implying that his primary opponent, Rep. Heather Wilson, is too liberal for New Mexico. "There's only one: only one conservative in the race for Senate," the ad says, crediting Pearce for being "the only New Mexico congressman to oppose a disastrous government-run socialized-medicine scheme" (a reference to the State Children's Health Insurance program, which Wilson supported).

The attacks became more explicit a week later, when Pearce's campaign released a second ad alleging that Wilson missed important votes in order to film negative campaign commercials. "Wilson missed doing the people's work, because she put her political ambition first," an announcer claims. For good measure, the ad's tagline -- "liberal values, liberal votes" -- adds the charge of liberalism to its accusations of congressional truancy.

But Wilson hadn't waited for this second ad in order to respond. Days after "Consistent Conservative" hit the air, she placed her first paid media of the race, a response ad accusing Pearce of running a negative campaign, and attacking him for voting against an expansion of the Border Patrol and not voting for a troop funding bill. (Pearce didn't vote against it either -- he was absent.)

Whichever Republican wins the nomination, the immediate beneficiary of the ad war will likely be Democratic candidate Rep. Tom Udall, a well -funded candidate who faces no opposition -- and no attack ads -- in his party's primary.