Why Was the Republican Field So Weak This Time?

It has been interesting to see the Republican primary process work itself out.  The party is clearly not satisfied with Mitt Romney, for whom they have been trying repeatedly to find a substitute.  None of the other flavors of the month which came and went were terribly strong.  Newt Gingrich, seemingly the last one standing, has generated panic among party powerful.  There have been calls for a savior to enter the race since it started and they continue, albeit somewhat muted at this late point.

There are stronger candidates that could have stepped up and chose not to -- Jindal from Louisiana, Christie from New Jersey, Daniels from Indiana, even McCain with another run.  During the process, there seemed to be a weakened incumbent, so why did the field that developed turn out to be so weak?  Is the threat of an incumbent so powerful that even with a bad economy, it seems too high of a mountain to climb?  Is there something amiss in the party recruitment apparatus?  Has the tea party fractured the GOP in such a way that the usual recruitment mechanisms don't work?  How did the Republicans come to have the field they did and not a stronger one, even in their own estimation?