“Blue Dog Democrats” = Democrats who campaign like conservatives, talk like conservatives, pretend to be conservatives ... until they turn blue in the face... and then do what the Democrat party bosses tell them to do, vote how the Democrat Party bosses tell them to vote and then go back home to claim they represented their voters well.
The definition provided by Charlie Stenholm when they created the moniker, "A Blue Dog Democrat is a Yellow Dog Democrat who has been choked."
They are not simply pro-life Dems, it is as you say, feint conservative in order to secure the seat, then fold, cave, vote as the Progressive/Liberal leadership require when it REALLY counts.