In Tuesday night’s Las Vegas debate, Texas Gov. Rick Perry answered a question about uninsured children in his state by attacking former Massachusetts governor Mitt Romney for once having undocumented immigrants at work on his lawn.

“And Mitt, you lose all of your standing, from my perspective, because you hired illegals in your home and you knew about it for a year,” Perry said, in a total non-sequiter.

Republican presidential candidates former Massachusetts Gov. Mitt Romney, left, and Texas Gov. Rick Perry speak during a Republican presidential debate Tuesday, Oct. 18, 2011, in Las Vegas. (Chris Carlson/AP)

The charge dates back to the 2008 presidential campaign. Basically, Romney hired a lawn company for his Belmont home that in a 2006 Boston Globe story was revealed to be employing undocumented immigrants from Guatemala. The former governor kept using the company for a year. Romney fired the company in 2007, when reporters found that illegal immigrants were still employed there. He said he had been promised (falsely) that the problem would be corrected.

In that 2008 primary, as in this one, Romney has made opposition to illegal immigration a major part of his campaign. In that race, he attacked Rudy Giuliani for failing to crackdown on undocumented immigrants New York City mayor.

Giuliani responded by hammering the landscaping issue, calling Romney’s home a “sanctuary mansion.” McCain joined in too, joking that “Maybe his solution will be to get out his small-varmint gun and drive those Guatemalans off his lawn.”

In a debate before the second Globe report came out, Romney flat-out denied having undocumented workers employed on his property.

In Las Vegas last night, Romney admitted that he was wrong, saying, “It is hard in this country as an individual homeowner to know if people who are contractors working at your home, if they have hired people that are illegal.”

Romney’s campaign is, predictably, dismissing Perry’s attacks.

“It's an old story,” said Romney adviser Eric Fehrnstrom. “If anyone has an illegal immigration problem, it’s Rick Perry.”

Revelations of undocumented employees have brought down campaigns, but the illegal workers are no longer employed by Romney, so it’s hard to see this as a lasting political problem.

And even when it was fresh campaign fodder, the scandal didn’t hurt Romney much. Old rivals say it was only a story for a few days.

“Ultimately it didnt become a huge issue,” said Michael DuHaime, who was Giuliani’s 2008 presidential campaign manager. “We moved on to issues that were ultimately more important to voters, and I think that will happen this time too.”

“My sense overall is that it did not have a significant impact on his campaign,” said Terry Nelson, McCain’s campaign manager in 2006 and 2007. “In some respects its probably due to a similar dynamic to what you see now, that there were much bigger issues related to immigration at the time.”

As in that campaign, neither Perry nor Romney has a perfect record as far as conservatives are concerned on the immigration issue. Perry backs in-state tuition for undocumented students; Romney used to support comprehensive immigration reform with a path to U.S. citizenship.

Worse than the Globe report might be Romney’s response to Perry’s insistent questioning Tuesday night, which implies that his concern with the company was more political than principled.

“So we went to the company and we said, look, you can't have any illegals working on our property,” said Romney. “I'm running for office, for Pete’s sake, I can't have illegals.”

The Democratic National Committee is already using that response in a web video.