The latest state by state polls show Arizona and Ohio as leaning to Kerry despite being won by Bush, with New Hampshire now a solid Kerry state. They also say Nevada and Florida are toss-ups, and at least one poll says Kerry is vulnerable in Pennsylvania.
Nader will always have an impact in the toss-up states, the ones that are likely to be decided by 1-2%. Most of the other battleground states, however, are not Nader's strong areas. For this and other reasons, the national polls will overstate Nader's influence.
But, without him in it last time, Gore would likely be President. So that impact in the toss-up states always counts.
