Michael Barone notes the strengths and weaknesses of the Republican party base.  Interesting in the article is the changing base of the party over the last few decades.  Snip:

Yet Republicans assembling sooner or later in storm-tossed Tampa should keep in mind that in 2008, as in 1944, their party was in the minority and that they need to add votes from other groups to win. White noncollege voters and white evangelical Christians were only 42% and 37%, respectively, of the winning Republican coalition in the 2010 congressional elections.

Recent polling suggests that affluent suburbanite Mitt Romney is making gains among groups where the party has been losing votes, and if he is elected he will need to govern in a way that holds this larger party together. But that is the challenge the Republican Party has always faced, and over its 158 years it has won more presidential elections than it has lost.