White House senior adviser David Axelrod tried Sunday to redirect Democratic criticism away from fears of foreign influence in campaign spending and toward the unsavoriness of mystery donors in general.

Outside groups favoring GOP candidates and causes are pummeling Democratic-leaning outside groups in spending. The administration has argued that because the groups are not required to disclose their donors, foreign money could be playing an illegal role in U.S. politics, but it has not been able to show evidence to back up the accusation.

Axelrod sought to make the broader point during an appearance on CNN’s “State of the Union” that voters do not know the source of the money behind the campaign ads of groups known as 501(c)s. The nonprofit organizations are not obligated to disclose donors if their primary mission is not political.

“They say, trust us, trust us, everything is cool, everything is kosher, don’t worry about it, but we’re not going to disclose. Let me tell you something, [if] people don’t disclose, there’s a reason,” Axelrod said.

He later said: “If they don’t want to disclose who their money is coming from, there’s a reason for that. And the reason is, they don’t want to say this ad was brought to you by Wall Street, who wants to repeal financial reform; this ad was brought to you by the health insurance industry, who wants to repeal health insurance reform; this ad was brought to you by the oil industry that doesn’t want to have to be responsible when they leak oil in the Gulf of Mexico.”

Axelrod also called into question whether the organizations truly have non-political primary missions. “It’s perfectly legal if they spend a majority of their money on something else. It will be interesting to see if that’s the case,” he said.

He criticized Republicans for opposing Democratic efforts to pass a campaign finance disclosure law this year, without directly answering questions about why Democratic-leaning outside groups are not voluntarily revealing their own donors. “I think that we believe deeply in disclosure, no matter who is running the ads,” he said.