In the Wall Street Journal, Larry Sabato analyzes the Electoral College:
Republicans therefore are a lock or lead in 24 states for 206 electoral votes, and Democrats have or lead in 19 states for 247 electoral votes. That’s why seven super-swing states with 85 electors will determine which party gets to the magic number of 270 electoral votes: Colorado (9), Florida (29), Iowa (6), Nevada (6), New Hampshire (4), Ohio (18) and Virginia (13).
Prior to Obama’s 2008 victories in each of these states, several had generally or firmly leaned Republican since 1980. Virginia, which hadn’t voted Democratic since 1964, was the biggest surprise, and its Obama majority was larger than that of Ohio, which has frequently been friendly to Democrats in past decades. Massive Hispanic participation turned Colorado and Nevada to Mr. Obama, and it helped him in Florida.
The GOP has gotten a quiet advantage through the redistricting following the 2010 Census. The Republican nominee could gain about a half-dozen net electors from the transfer of House seats—and thus electoral votes—from the northern Frostbelt to the southern and western Sunbelt. Put another way, the Democrats can no longer win just by adding Ohio to John Kerry’s 2004 total. The bleeding of electoral votes from Democratic states would leave him six short of 270.
More here.