(CNN) Former Rep. Darrell Issa launched an exploratory committee to run for a congressional seat now held by another California Republican, Rep. Duncan Hunter, who is facing federal corruption charges.

"I have formally launched an exploratory committee for the 50th Congressional District in California," wrote Issa on his campaign website . "I have received such a tremendous outpouring of encouragement from supporters inside the district, and around the state and across the Nation. I'm truly grateful for the many encouraging phone calls, messages and letters that I have received."

Issa, the former chairman of the House Oversight committee, was a constant gadfly to the Obama administration, overseeing investigations and contentious hearings into the attack on the US embassy in Benghazi, Libya, and on the Internal Revenue Service's targeting of conservative groups, amid other issues.

Last year, President Donald Trump nominated Issa to run the US Trade and Development Agency.

The nomination seemed to stall for months, but Senate Foreign Relations committee chairman Jim Risch told CNN in August that he planned on holding a hearing on it in September, saying Issa was well qualified for the role.

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