David Wasserman at 538 had an interesting article on how blue state Republican voters are essentially over-represented in GOP convention delegate counts. The reason is that many states allocate based on congressional district so that whether you have a lot of Republican voters or a little, your district will be getting the same number of delegates. The thinking goes that the reason we end up with Presidential candidates who are to the left of the rest of the party and especially the Congressional delegation is because of this over-representation.
While the fact that blue state GOP voters are over-represented seems like it is most definitely true, that doesn't mean that they have an outsized impact on the result of the nomination process. It would be true if we had a national primary with every state going to the polls at once, but we don't we have that, we have a sequential process. Because of that, there is a certain amount of path dependence. In other words, sure you might be the perfect candidate for delegate heavy NY and CA, but if you don't survive the few few primaries and caucuses, you'll never get there and those voters will never get to even get to choose to vote for you. I know because I live in blue NJ and there isn't even a competitive race once it gets to me.
Most nominating contests are decided before April and sometimes much earlier (note that by this point 1,539 out of the 2,472 [or 62%] delegates would be chosen), so I decided to use only the contests from February and March to see how many delegates come from red states and how many from blue. In this case, I defined a red state as one that went to Romney in 2012 and a blue one was one that went to Obama. What I got was that 586 out of the 1,539 delegates come from blue states and 953 delegates come from red states. So by April 1, only 38% of the delegates will have come from blue states.
But even that analysis is probably overstating blue state influence mainly because many states aren't blue or red but are purple swing states. You just can't equate Iowa, where Obama won with 52% of the vote, to New York, where he won with 63%. So for any state where either Obama or Romney won it with 52% or less of the vote, I dubbed to be a purple state. In that analysis, 289 of the delegates chosen before April are from blue states, 369 are from purple and 881 are from red states. So blue state GOP voters are only 18.8% of that total. And importantly, none of the states with contests in the month of February, IA, NH, SC and NV are blue and it will be almost impossible for any candidate who can't win in those states to make it to states like New York and California. And it doesn't get any easier after that really. There will be 624 delegates chosen on March 1, 479 of which will be from deep red states such as Texas and Alabama. Only 96 delegates on that date will be in blue states like Massachusetts and Vermont. Unless a blue state wunderkind can win in IA or NH, they will face a very hard slog through the end of March.
Here is a handy dandy chart with cumulative delegate counts by red state vs. blue vs. purple