You don't suppose the senate castigating every Protestant candidate the Protestant president proposed might have anything to do with it, do you?
http://www.ask.com/wiki/Religious_Affiliation_in_the_United_States_Senate says that for the 111th Congress, the makeup of the Senate is:
Catholic: 26; Presbyterian 13; Jewish 13; Methodist 10; Baptist 7; LDS 5; Lutheran 2; UU 1; other Protestants the remainder. So, we have 61 Protestant Senators. Why would they castigate their own? They didn't in the 1800s and 1900s.