Schaffer represented Colorado's 4th Congressional District for three two-year terms before leaving Congress in 2002 because of a self-imposed six year term limit.
"I will take the next few days to meet with family, friends and advisers to set organization and strategy for the U.S. Senate race," Schaffer said. "I have an excellent team in place and I look forward to returning the hundreds calls from folks across our great state."
Schaffer's name began to circulate as a potential candidate shortly after Gov. Bill Owens announced Tuesday he would not run for Campbell's seat. Other Republicans said to be considering the race include 3rd Congressional District Rep. Scott McInnis and 7th Congressional District Rep. Bob Beauprez.
A formal announcement of Schaffer's candidacy is expected by the end of the week.