The four Senate and House defense oversight committees will look very different when the new Congress is seated in January, after Republicans took control of the Senate and gained more seats in the House than many polls previously suggested. On the Senate Armed Services Committee, Sen. John McCain (R-Ariz.) is poised to take over as chairman. Current Chairman Carl Levin (D-Mich.) is retiring, and subcommittee chairmen Mark Udall (D-Colo.) and Kay Hagan (D-N.C.) lost their elections, leaving a vacuum in…