Newt Gingrich
The Republican Speaker of the House of Representatives from 1995 to 1999, he was one of the architects of the fiscal discipline that was achieved during the '90s.

Allan Hubbard
Director of the National Economic Council from 2005 to 2007, he served as President Bush's point man on Social Security reform.

Paul O'Neill
Treasury Secretary from January 2001 to December 2002, he was forced to resign over his differences with the Bush administration's tax cuts and Iraq policy.

Peter Orszag
Director of the Office of Management and Budget, he previously served as director of the Congressional Budget Office from 2007 to 2008.

Gene Sperling
Director of President Clinton's National Economic Council, he helped craft the Deficit Reduction Act of 1993.

David Walker
Former comptroller general of the United States, he's president and CEO of the Peter G. Peterson Foundation, a nonprofit that advocates action on the national debt.