DJ Drummond discusses the 2008 race. I believe he is correct in some areas on this.
That said, the GOP faces two risks. One is to nominate a complete drone like Lincoln Chafee or Olympia Snowe. The other is if a hard-liner gets elected. As we saw in the mid-terms, the conservatives alone cannot win an election. They need to be competitive among moderates, small-l libertarians, and Hispanics to be able to reliably win a presidential race.
The "big three" frontrunners, Mitt Romney, John McCain, and Rudy Giuliani, all can ensure that to one degree or another - and that will make 2008 a win for all three branches.