Council on Foreign Relations (CFR):
- Former Sen. Howard Baker (R-TN): Member of CFR
- Sen. Olympia Snowe (R-ME): Member of CFR
- Former Sen. Tom Daschle (D-SD): Member of CFR
- Rep. Geoff Davis (R-KY): Member of CFR
- Former Sen. Christopher Dodd (D-CT): Member of CFR
- Rep. David Dreier (R-CA): Member of CFR
- Sen. John Kerry (D-MA): Member of CFR
- Sen. Joe Lieberman (I-CT): Member of CFR
- Sen. John McCain (R-AZ): Member of CFR
- Former Sen. John Warner (R-VA): Member of CFR
- Former Rep. Tom Foley (D-WA): Member of CFR
- Former Rep. Harold Ford (D-TN): Member of CFR
- Former Rep. Newt Gingrich (R-GA): Member of CFR
- Former Sen. Chuck Hagel (R-NE): Member of CFR
- Former Rep. Lee Hamilton (D-IN): Member of CFR
- Former Rep. Jane Harman (D-CA): Member of CFR
- Former Sen. Gary Hart (D-CO): Member of CFR
- Del. Eleanor Holmes Norton (D-DC): Member of CFR
Third Way:
- Rep. James Clyburn (D-SC): Honorary Co-Chair
- Rep. John Dingell (D-MI): Honorary Co-Chair
- Rep. Ron Kind (D-WI): Honorary Co-Chair
- Rep. Joseph Crowley (D-NY): Honorary Co-Chair
- Rep. Allyson Schwartz (D-PA): Honorary Co-Chair
- Rep. Jared Polis (D-CO): Honorary Co-Chair
- Sen. Thomas Carper (D-DE): Honorary Co-Chair
- Sen. Claire McCaskill (D-MO): Honorary Co-Chair
- Sen. Mark Udall (D-CO): Honorary Co-Chair
- Sen. Jeanne Shaheen (D-NH): Honorary Co-Chair
- Sen. Kay Hagan (D-NC): Honorary Co-Chair
- Sen. Chris Coons (D-DE): Honorary Co-Chair
- Former Rep. Ellen Tauscher (D-CA): Co-Chair
- Former Rep. Gabrille Giffords (D-AZ): Emeritus
- Former Rep. Jane Harman (D-CA): Emeritus
- Former Sen. Blanche Lincoln (D-AR): Emeritus
- Former Sen. Evan Bayh (D-IN): Emeritus
- Former Rep. Melissa Bean (D-IL): Emeritus
- Former Sen. Mark Pryor (D-AR): Emeritus
Bipartisan Policy Center (BPC):
- Former Sen. Howard Baker (R-TN): BPC Founder
- Former Sen. Tom Daschle (D-SD): BPC Founder
- Former Sen. Bob Dole (R-KS): BPC Founder
- Former Sen. George Mitchell (D-ME): BPC Founder
- Former Sen. Chuck Robb (D-VA): BPF Board of Directors
- Former Sen. Robert Bennett (R-UT): BPC Senior Fellow
- Former Rep. Sherwood Boehlert (R-NY): BPC Senior Fellow
- Former Sen. John Danforth (R-MO): BPC Senior Fellow
- Former Sen. Pete Domenici (R-NM): BPC Senior Fellow
- Former Sen. Byron Dorgan (D-ND): BPC Senior Fellow
- Former Sen. Bill Frist (R-TN): BPC Senior Fellow
- Former Rep. Richard Gephardt (D-MO): BPC Senior Fellow
- Former Rep. Dan Glickman (D-KS): BPC Senior Fellow
- Former Sen. Slade Gorton (R-WA): BPC Senior Fellow
- Former Sen. Trent Lott (R-MS): BPC Senior Fellow
- Former Rep. Christopher Carney (D-PA): Panel Member of BPC's Homeland Security Project
Center for Strategic & International Studies (CSIS):
- Former Sen. Sam Nunn (D-GA): Chairman of the Board of Trustees and Counselor at CSIS
- Former Sen. Bill Frist (R-TN): CSIS Trustee
- Former Sen. John Warner (R-VA): CSIS Counselor
- Former Sen. William Brock (R-TN): CSIS Counselor
- Rep. Howard Berman (D-CA): CSIS Advisory Board
- Rep. David Dreier (R-CA): CSIS Advisory Board
- Sen. Dianne Feinstein (D-CA): CSIS Advisory Board
- Sen. Kay Bailey Hutchison (R-TX): CSIS Advisory Board
- Sen. Richard Lugar (R-IN): CSIS Advisory Board
- Sen. John McCain (R-AZ): CSIS Advisory Board
- Sen. Jack Reed (D-RI): CSIS Advisory Board
- Sen. John Rockefeller (D-WV): CSIS Advisory Board
Atlantic Council of the United States (ACUS):
- Former Sen. Chuck Hagel (R-NE): Chairman of the Atlantic Council of the United States (ACUS)
- Former Sen. John Warner (R-VA): Honorary Director of ACUS
- Former Rep. Ellen Tauscher (D-CA): Director of the International Advisory Board at ACUS
- Sen. Mark Warner (D-VA): Director of the International Advisory Board at ACUS
- Former Rep. John Tanner (D-TN): Director of the International Advisory Board at ACUS
German Marshall Fund (GMF):
- Former Sen. Robert Bennett (R-UT): German Marshall Fund (GMF) Board of Trustees
- Former Rep. Robert Wexler (D-FL): GMF Board of Trustees
- Former Rep. Jim Kolbe (R-AZ): GMF Senior Transatlantic Fellow
- Former Rep. Glenn Nye (D-VA): GMF Senior Transatlantic Fellow
- Sen. Richard Lugar (R-IN): He will become a GMF Senior Transatlantic Fellow
Brookings Institution:
- Former Rep. Lee Hamilton (D-IN): Brookings Honorary Trustee
- Former Rep. Bill Frenzel (R-MN): Brookings Guest Scholar
- Former Rep. Dick Gephartdt (D-MO): Brookings Hamilton Project Advisory Council Member
- Former Rep. David Dreier (R-CA): Brookings Distinguished Fellow
Center for American Progress:
- Former Sen. Tom Daschle (D-SC) is a Distinguished Senior Fellow at the Center for American Progress (CAP).
- Former Rep. Tom Perriello (D-VA) is the President and CEO of the Center for American Progress Action Fund (CAPAF). He is also Counselor to CAP.
- Former Rep. Brad Miller (D-NC) is a Senior Fellow at CAP.
- Former Rep. Patrick Murhpy (D-PA) has been named a Senior Fellow at the Center for American Progress (CAP).
Heritage Foundation:
- Former Rep. Ernest Istook (R-OK): Heritage Foundation Distinguished Fellow
- Former Rep. Jim Talent (R-MO): Heritage Foundation Distinguished Fellow
- Former Rep. John Shadegg (R-AZ): Heritage Foundation Distinguished Fellow
Wilson Center:
- Former Rep. James Leach (R-IA): Wilson Center Public Member
- Former Rep. Jane Harman (D-CA): Wilson Center Director/President/CEO; Aspen Institute Board of Trustees
- Former Sen. Hillary Clinton (D-NY): Wilson Center Public Member
American Security Project (ASP):
- Former Sen. Gary Hart (D-CO) is the Chairman of the American Security Project (ASP)
- Former Sen. Chuck Hagel (R-NE) is on the Board of Directors of ASP
- Sen. John Kerry (D-MA) is on the Board of Directors at ASP
American Enterprise Institute (AEI):
- Former Sen. Jon Kyl (R-AZ): AEI Visiting Fellow and Co-Chair of the American Internationalism Project.
- Former Sen. Joe Lieberman (I-CT): Co-Chair of the American Internationalism Project.
- Former Rep. Newt Gingrich (R-GA): Former Senior Fellow at AEI. He is a member of the Terrorism Task Force at the Council on Foreign Relations (CFR).
- Former Sen. Phil Gramm (R-TX): AEI Visiting Scholar.
Others:
- Former Rep. Ike Skelton (D-MO): Center for a New American Security (CNAS) Board of Advisors
- Former Sen. Bill Bradley (D-NJ) has contributed financial support to the Carnegie Endowment for International Peace (CEIP).
- Former Sen. Sam Nunn (D-GA) is the Annenberg Distinguished Visiting Fellow at Stanford's Hoover Institution.
- Former Rep. Jim Marshall (D-GA) has been named as the new President of USIP.
- Former Rep. Robert Wexler (D-FL) is the President of the S. Daniel Abraham Center for Middle East Peace.
- Former Rep. Phil Sharp (D-IN) is the President of Resources for the Future (RFF).
- Former Rep. Ron Paul (R-TX) started his own think tank called the Ron Paul Institute for Peace and Prospertiy.
Governors and former governors are also affiliated with various think tanks. Current and former Cabinet members are also affiliated with think tanks.
Here is a Muckety Map showing some think tank-Congress connections.