Plus, according to a Perry source, there was an added bonus: by going after Romney personally — the accusation has to do with Romney’s own house — they saw the potential to make Romney react the hardest…

Perry’s senior political adviser Dave Carney said in the post-debate spin room that Romney’s vulnerability on the issue is clear.

“When you make a holier-than-thou argument about it and you know about hiring illegals … it seems kind of hypocritical,” Carney said.

For the last few weeks, Perry was under attack for his own position on immigration — opposing a border fence and providing in-state tuition for illegal immigrants at Texas colleges — but an offensive defense personal attack is a Perry campaign staple. He did it in his 2010 re-election race, for example, when he turned to calling his primary opponent Sen. Kay Bailey Hutchison a tool of Washington to rebut his own $300,000 in travel expenses for his own D.C. campaign events.