Beck said that's what has scared politicians off in the past from addressing the country's immigration levels, adding that the timing of the ad was intended to encourage the GOP candidates to focus more on jobs than they have in previous debates.

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While immigration has been a common topic in the GOP race so far, the conversation has focused on criticizing illegal immigration, which poses less of a backlash risk for politicians because it involves breaking the law. But candidates in this and other elections have avoided drawing connections between legal immigration and unemployment, being careful not to offend minority constituency groups such as Hispanics, one of the fastest growing voter blocs.

NumbersUSA said it has slightly modified the original ad that aired in targeted markets to broaden it for a national audience. The group hasn't disclosed what it's spending on the ad.

"The public reacts very, very differently when you talk about legal and illegal immigration," said Tamar Jacoby, president of ImmigrationWorks USA. "Generally the public is for legal immigration."

Jacoby noted that even with high unemployment, the United States still needs immigrant labor to be competitive with other countries. But she acknowledged that 1 million sounds daunting to many Americans.

"In an economic downturn, I won't be surprised if the ads do feed into people's fears," she said.


—This post was updated at 4:45 p.m.