I hate to revive this thread, but I hate it much less than starting another "MUH POPULAR VOTE" thread.
My basic issue with a national popular vote to elect the President is that it fundamentally changes the question asked of presidential candidates. Right now, the balance of power is controlled by the center of the electorate in a couple of crucial battleground states such as Ohio or Wisconsin, or by the generally moderate electorate of states like New Hampshire. It forces candidates and campaigns to play to those voters. That's the mandate of the electoral college. Win people outside your base.
A national popular vote, however, changes the mandate. Instead of trying to win the moderate suburban family vote with moderate education and tax relief proposals, Republicans will spend their time throwing as much reasonably red meat as possible to make sure every white in the Deep South votes. Instead of governing to the economic center-right to right, Republicans would govern on base motivators that divide the country. Likewise, Democrats will move to a very turnout-based idea of elections. It'll be about getting as many of your folks to show up as possible. The electoral college forces candidates to moderate.
This is only the case if the swing states are more "moderate" than the country as a whole (having lots of swing voters and relatively few "base" voters). This may be true in New Hampshire, but not so much North Carolina. Overall I think it's about the same. If it's a good electoral strategy to pander to the most conservative 10% of the electorate in the USA, it's probably also a good electoral strategy to pander to the most conservative 10% of the electorate in Ohio (who are probably similarly conservative). Breaking up the electorate into microcosms doesn't fundamentally change anything about electoral strategy.