Damo, I don't know what you expected.  
A victory margin of 15 to 20 points???  To my knowlege, those types of landslides never happen except in the case of an extremely popular incumbent versus a flawed and unviable opposition candidate.  
Which didn't apply to this election.   Say what you will about McCain, but he was a viable candidate.  The only viable candiate the repugs could have nominated.  The only dude that could have run against his own party.  LOL.   
So the 2008 election was for a democrat who opposed the GOP, and a republican who claimed he was running against the GOP, in effect.  LOL. That hardly supports your argument that there is substantial republican strength. 
I really don't think losing 80 house seats, 15 senate seats, and a presidential blowout on the scale of the Dukkakis blow out, over the last two years, is a sign of relative republican strenght. 
But, if republicans think there isn't anything fundamentally wrong with their party, I'm cool with that.