The day after his would-be campaign manager was replaced, Ex-Sen. Fred Thompson has another senior staff position to refill.

J.T. Mastranadi was hired just a week and a half ago to be the campaign's director of research. He resigned this morning, a friend of his said. The friend said that Mastranadi was "fed up" with the "lack of structure" and was unclear about his role in the coming campaign.

Thompson's spokesperson, Linda Rozett, confirmed that Mastranadi submitted his resignation this morning. "He did it for personal reasons," she said.

Mastranadi was a former NRSC research director and is considered one of the best investigators in the business. Most recently, he worked with Thompson friend David Bossie on an anti-Hillary Clinton documentary.

Rozett dismissed the significance of the second resignation in two days.

"Everything is on track," Rozett said. "Friends of Fred Thompson continues to add people."