Bennett, a Republican, reportedly earns $2,000 a month for his work on the Cancer Treatment Centers of America board. The for-profit company was started in 1988 by Richard Stephenson, who also sits on the board of the prominent Tea Party group FreedomWorks. KTVK reports that Bennett has received tens of thousands of dollars from Stephenson's company.
Bennett denies any conflict of interest from his work on the board.
"I don't think there's anything inappropriate, in fact it's an honor for me to serve on a board that’s helping treat people for cancer," he said. "I'm on other boards, my whole life isn't about being secretary of state."
However, progressive groups in the state are raising eyebrows at the Republican's ties to the Tea Party activist.
"We known that FreedomWorks and Mr. Stephenson are engaged in electoral politics, there appears to be a real conflict of interest," Arizona Advocacy Network director Sam Wercinski said.
Stephenson, a reclusive millionaire from Illinois, was at the center of an internal battle over FreedomWorks' leadership last fall. According to the Washington Post, Stephenson agreed to pay chairman Dick Armey $400,000 annually over 20 years if Armey would agree to leave the group.
The Post also reported that Stephenson helped funnel over $12 million in donations to the group through two Tennessee corporations, a move that drew the ire of campaign finance watchdog organizations.
Despite his active involvement in FreedomWorks, the Arizona Secretary of State said he doesn't consider Stephenson to be "political activist."
Bennett, who took office in 2009, is exploring a run for Arizona governor next year. KTVK reports that Stephenson and other board members at the Cancer Treatment Centers of America have made significant donations to Bennett's exploratory committee.
Last spring, Bennett drew national headlines when he requested that Hawaiian officials verify President Barack Obama's birth certificate. He later apologized for the inquiry.