The swing states, are big political playground with a lot of electoral votes that can vote either way. The Republicans never won the Presidency without winning Ohio. Historically the candidate that wins Ohio and Florida gets the White House.
Three surveys from NBC/Wall-Street/Marist. You need 270 electoral votes to win the race.
Florida (29 votes)
Virginia (13 votes)
Ohio (19 votes)
All states Bush won in 2004.