Aaron Weaver, has posted some analysis on the church affiliation claimed by members of the 111th US Congress. He makes special note of incoming legislators affiliated with Baptist churches.
He states that 27 House Representatives hold membership in a Baptist church that affiliates with the Southern Baptist Convention. He also lists four SBC affiliated Senators.
Southern Baptists in the Senate include John McCain (R-AZ), North Phoenix Baptist Church; Roger Wicker (R-MS), First Baptist Church Tupelo; Tom Coburn (R-OK), First Baptist Church Muskogee; and Lindsey Graham (R-SC), Corinth Baptist Church, Seneca.
Weaver notes this information is supplied by the legislators, not by the official church records. So there may be a few like McCain who are not actually members, but merely self-identified attendees.