Vegas vitriol

Moderator Anderson Cooper opened Tuesday evening's CNN debate in Nevada by saying he would not use bells or buzzers, but would depend on a polite verbal cue. But politeness was not this debate's strong point.

Candidates went after each other with vigor under Cooper's questioning, which seemed calculated to unrelentingly pit the candidates against each other in pairs. Voting starts in earnest in just two and a half months, and the candidates didn't need much prodding to compare and contrast. A boisterous exchange between Mitt Romney and Rick Perry is the moment most viewers will remember.

Perry, positioned beside Romney, made a concerted effort to regain an advantage on immigration policy and was a more active part of this debate co-sponsored by the Western Republican Leadership Conference. He bluntly accused Romney of hiring illegal immigrants, a charge that Romney explained away as a lawn-care contractor, adding that it could have been prevented by an e-verify system, which he then said Perry opposed. Speaking over each other, Romney gained the time he needed for an explanation by insisting Perry stop needling him during his time.

Despite an early and lengthy platform-wide exchange with Herman Cain about the merits of the sales tax portion of his 9-9-9 plan, it was telling that candidates repeatedly came back to Romney for the rest of the night, indicating perhaps that they still perceive the former Massachusetts governor as the frontrunner. Since he was allowed a response to every mention, it seemed to keep him in the spotlight more consistently than any of his rivals.

The Romney-Perry exchanges came in Nevada, an early caucus state that Romney ran away with in 2008 and only Perry has appeared to contest this time. Romney proposed that the long standoff over storing nuclear waste at Nevada's Yucca Mountain could be solved with compensation significant enough for a state to choose to accept the unwanted waste. Perry also played to the home crowd by specifically highlighting mining opportunities in Nevada he said the Obama administration blocked.

Perry also sidestepped a Baptist pastor's comments about Mormonism, simply saying he disagreed and he had said so. Romney nodded his acceptance, both offering limited comments about the role of faith in public life, as Newt Gingrich and Rick Santorum highlighted the importance of faith in general terms. Tuesday's forum was not focused on social conservative issues.

The debate moved along at an attention-keeping clip after the candidates were introduced like a sports team's starting lineup, and advertising interruptions were limited. Cooper also did a good job of not making himself the center of attention, with CNN largely keeping the cameras on the candidates.

Cain defended against attacks on his 9-9-9 plan as "apples to oranges" comparisons while opponents said it caused a double sales tax in states that already have a sales tax. Romney expressed concern about a "bushel basket" of taxes. Gingrich defended Cain and disagreed with his proposal in the same sentence, noting that Cain's "specific, very big idea" at least generated real debate over a topic that matters.

From the far end of the stage, Santorum managed to get into several prolonged dust-ups, including an early one baiting Romney's credibility over healthcare policy. Cooper let the two extensively hammer it out, a bonus to Santorum, while Romney defended his record as a state-level solution.

Santorum also had an exchange with Ron Paul, as he does seemingly every debate, since they represent polar opposite lines of conservative thought on issues such as defense spending. From the other end, Michele Bachmann could be heard calling out "Anderson" for a chance to get her message out.

Gingrich got the last word of the night, a gentle dig at the "bickering." The former speaker of the House again was rarely a target despite a gradual uptick in his polling strength in recent weeks. He only once took issue briefly with Romney, an exchange that probably harmed neither when Romney pointed out that Gingrich had once agreed with a Heritage Foundation concept that was used in Massachusetts. Even while criticizing Romney's healthcare record as "big government," Gingrich-perhaps thinking of the general election-admitted Romney's plan differed from Obama's.

Perry also contrasted with Bachmann about the merits of a border fence. "There's a better way," Perry said, calling for strategic fencing, boots on the ground, and drones in the air. Perry said a border-long fence costs too much and takes too long. Bachmann urged a fence, English as the official language, and no benefits for anyone in the country illegally. It was immediately after those remarks that Romney cautioned that the GOP candidates are enthusiastic about legal immigration.

Perry twice delivered his message on energy policy and foreign aid with more clarity than previous debates. "We've got 300 years of resources right under our feet in this country," he said. Perry advocated for reducing foreign aid, and strongly urged "discussion" of defunding the United Nations. Paul would cut foreign aid across the board, while Bachmann differentiated that she would preserve Israel's aid.

Paul, Santorum, and Gingrich all hit applause lines on defense policy, despite disagreeing with each other. Santorum favors cutting not one penny from the federal government's "first duty," while Paul advocates bringing the troops home and shutting down the foreign military bases of an unaffordable empire. Gingrich said it is "suicidally stupid" to tie defense to an arbitrary budget, and got a laugh with his line: "I'm a hawk, but I'm a cheap hawk."

One GOP candidate was able to avoid the verbal sparring Tuesday night. Jon Huntsman boycotted the Nevada debate because he says the state has unfairly moved the date of its presidential caucuses, forcing New Hampshire to change the date of its traditional first-in-the-nation presidential primary.