I have read a study someone compiled on the differences between the popular vote and the vote on the vote on the state that put the winning candidate over the top. Too busy to dig it up at the moment..but the results were that if you list the states a winning Presidential candidate won, starting from the one they won by the biggest percentage first and then then next biggest percentage and so forth...when you got to the state that put him over the half way point in electoral college...i.e. the state that put him over and secured victory...the percentage difference in vote of that state is almost always very close to the national popular vote!
Yes the national polls are very reflective of which way the electoral college will go. The only time you have splits is when it is very close as in 2000.