This is pure unadulterated poppycock!
“the 2008 race was going to the Democrats and the Republicans did not want a leading candidate for 2012 to lose or be roughed up during the campaign.”
Republicans don’t plan that well, but by the law of unintended consequences they managed to get Sarah Palin destroyed for 2012. Most of the time stuff just happens.
Who was our candidate in 1976? Why?
In case you have temporarily forgotten, it was Bob Dole. He had been a staunch Republican conservative and Senate leader. Although few thought he had a chance most thought he deserved it. A key consideration was that Clinton had the election sown up, this was before Lewinsky was revealed, and so Dole was offered as the sacrificial lamb.
As far as Sarah Palin is concerned it brought her out of the shadows and into the spotlight. Without McCain we may never have heard of Palin. Now she is a leading light of the conservative movement and may well have a great chance in 1012.
Needless to say, I disagree with your entire premise.