“I took the 55 Republican senators that served in the 109th Congress from 2005 through 2007 and divided them into two groups, moderates and conservatives, according to their voting records as analyzed by the statistical system DW-Nominate,” writes New York Times blogger Nate Silver on FiveThirtyEight.
… “Of the 27 moderates, at most six will return to the Congress in 2013: Mr. McCain, Susan Collins of Maine, Lisa Murkowski of Alaska, Thad Cochran of Mississippi, Lamar Alexander of Tennessee and Charles E. Grassley of Iowa.”