GOP strategist and fundraiser Karl Rove said Sunday that Crossroads GPS follows the law "very closely" when it comes to political activity.
"The leadership knew right from the get-go they were going to be looked at closely," Rove said on ABC's "This Week."
"So the laws and rules that the IRS has promulgated for decades were followed very closely by GPS for exactly that."
Rove cofounded the group in 2010, and it's played a large role in subsequent elections, spending millions on ads against Democratic candidates.
501(c)(4) groups of all political stripes are classified as "social welfare" groups. They defend their campaign efforts as legal because those efforts are often less than 50 percent of the groups' total activity.
Rove rebuffed criticism of Crossroads GPS on Sunday by saying similar groups on the left endure less scrutiny.
"There was no criticism from the left in 2000 when the NAACP voter fund spent $10 million to run an ad accusing George Bush of being a bigot," Rove said.
"No concern on the left when Americans United for Change ran television ads targeting Republican senators."