We hear a great deal about Republicans “marching in lock-step” — always in lock-step, those militant Republicans! — but, as well-informed Congress-watchers know, Republicans are in fact less likely to vote with their party than are Democrats.
As Derek Willis notes, retiring Senator Barbara Boxer of California voted with her party 98 percent of the time in the 113th Congress, and even that remarkable figure made her only the 27th-hackiest partisan hack on the Democratic side of the aisle.
Of course, voting with one’s party is excellent — if one’s party supports good things. Senator Boxer’s party mainly does not.