Fred Thompson shakes up his "unofficial" campaign

Although not an official candidate for President, former Tennessee Senator and NBC's "Law & Order" actor Fred Thompson (photo) is shaking up his unofficial campaign by replacing his top aide.

Concerns over his wife, Jeri's involvement in his unofficial campaign, former Michigan Senator and Secretary of Energy Spencer Abraham and Florida GOP strategist Randy Enright, will run his political operation.

Thompson, 64, is establishing a ''testing the waters'' committee that allows him to raise money for a presidential bid, with an official launch likely in September, after the Labor Day holiday. Although Rudy Giuliani, Mitt Romney and John McCain head the nine-man GOP field, Thompson often registers in double digits in public opinion polls.

Thompson has raised several million dollars, hired staff and visited early primary states such as New Hampshire and South Carolina.