The group California Common Cause is asking California's campaign finance watchdog to investigate the donors behind an $11 million political contribution from a nonprofit based in Arizona called Americans for Responsible Leadership.

The money went to an Orange County-based Political Action Committee that is active in the fight over two initiatives on California's November ballot.

California common cause called the donation from Americans for Responsible Leadership possibly the largest "secret political donation in California history."

Today, Common Cause asked the California Fair Political Practices Commission to investigate. It cited a campaign finance law that requires groups to disclose the source of money used for political activity.

The Arizona-based group gave the donation this week to a PAC that is campaigning against Governor Jerry Brown's tax initiative and in favor of an initiative to erode union power.