Rutherford, a Republican from Chenoa, says Illinois first needs to see how the economy does after Gov. Pat Quinn signs a capital construction bill. The bill is supposed to create jobs.
Giannoulias has said that he wanted to run for the U.S. Senate to replace Roland Burris, who has opted not to run for a full term.
Rutherford has run for statewide office before. He lost an election for secretary of state against incumbent Jesse White in 2006.