SACRAMENTO — California’s campaign finance watchdog sued an Arizona nonprofit group Thursday, escalating the battle over a controversial $11-million political donation.

The Fair Political Practices Commission is seeking records, ranging from financial statements to text messages, as part of an effort to unmask the nonprofit’s donors, who have been accused by activists of improperly hiding their identities.

A California regulation says nonprofits cannot conceal a donor’s identity if the contribution was intended for a state campaign. The $11 million went to the Small Business Action Committee, which is fighting Gov. Jerry Brown’s tax campaign and pushing a ballot measure to curb unions’ political influence.

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