[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/09/28/art.whitmantech.gi.jpg caption="An adviser to California Republican Meg Whitman questioned the 'mental condition' of Whitman's opponent Monday."]
(CNN) – A top aide to a California Republican gubernatorial candidate called into question a rival candidate's "mental condition" Monday, in what has become an increasingly bitter battle for the GOP nomination.
Mike Murphy, a political adviser to former EBay CEO Meg Whitman, was responding to an accusation by California Insurance Commissioner Steve Poizner, who accused Murphy of "intimidation tactics" in an effort to convince him to drop out of the race.
"[A]ll I can say is that I'm starting to worry about Commissioner's mental condition," Murphy said in a statement.
Specifically, the Poizner campaign said that Murphy contacted a senior member of Poizner's political staff to try and convince the commissioner to leave the race and focus on challenging Democratic Sen. Dianne Feinstein in 2012. The Poizner campaign added that Murphy sent an e-mail after the telephone call suggesting Whitman was willing to spend tens of millions of dollars "'tearing up'" Poizner.
"The Murphy e-mail has been sent to the proper authorities, including the FBI, the U.S. Attorney's office, and the Attorney General's office for review of ethical violations," the Poizner campaign said in a statement.
Murphy does not dispute contacting Poizner's campaign pollster, who he described as an "old friend" as well as another Poizner adviser.
"It is true that I have been trying to find a way to avoid a costly and unnecessary Republican primary," Murphy said.
While Murphy said he will cooperate with law enforcement authorities, the Whitman adviser added he has no plans to speak publicly on the subject again.
"I do not plan to make any further comment on these discussions, as I do not want to create even more embarrassment for his consultants, or get anybody fired," Murphy said.
A recent poll showed that Whitman held a 28 percentage point lead over Poizner.