The reason for the downward trend of the GOP has been the abandonment of the party's conservative message. GOP moderates have been trying to take control of the party ever since the Pubbies were outmaneuvered by Clinton during the 95-96 budget battle. Conservatives gave the Repupublicans the majority in '94, so a lack of enthusiasm on the right will almost certainly lead to a loss of power for the party.
The conservative wing of the party did NOT cause the 94 change-over to Republican. In fact just the opposite- conservatives are always going to show up at the polls- it's the center, with some Democrats that came to the polls in 94 to elect Republicans. The truth of the matter is that the moderate voters caused Congress to change over to Republican in 94.
The Republicans have spent more in Congress in the last few years than at anytime in history except the 1970's. That's not why they are in decline- that's why they have barely hung on--- doling out the pork-- that's what kept the house in DEM hands for 40 years- pork pork pork-- that's what it's all about at the capital for the most part anyway.
What's stupid about Republicans is that they haven't "got it" yet- the political rhetoric you need to stay in power, and their political advisors are whack cases.