Who would you say was the conscience of the Republican party in 2012? What were they arguing for? Serious question, not American, follow their politics from afar.
Democrats lost their conscience with Clinton.
The last republican president with a clear conscience was probably Bush Sr. He was also crucified for it (hence the single term). He foolishly let reason about running a government get in the way of party bluster and that ended his career.
Carter was the last democrat president with a conscience and he also was lambasted for it.
Unfortunately in the US, principles and conscience haven't resulted in party success in the last 50 years.