I too think the polls are wrong, but in the other direction. Most polls are overestimating Republican turnout by weighting them more heavily in the sampling than is warranted by registration. The other mistake the polls are making is the question they're asking.
Most polls currently ask Obama or McCain. Obama has a solid lead in a two way race, but it isn't a two way race. There are Third Party Candidates this year, like every year. As Teddy Roosevelt, Ross Perot and Ralph Nader will tell you, they can have a profound effect on an election even if they don't capture a sizeable proportion of the vote. A poll from Colorado today illustrates my point.
When asked Obama or McCain, the poll results are
Obama - 51
McCain - 47
Undecided - 2
Nice. Obama clearly in the lead.
When asked who, including third party candidates, the results are
Obama - 50
McCain - 43
Barr - 3
Nader - 3
McKinney - 1
McCain drops 4 points while Obama only 1. If this pattern were to hold nationwide, Obama is in landslide territory, possibly even over the 383 I'm currently expecting for him.
It seems that when third party voters are asked the 2 person question liberals are saying "undecided" while conservatives are saying "McCain".
If Barr were to get more exposure nationally, or even in the battleground states, I'm betting his numbers would go much higher. Nader is polling around where he did last time, so I wouldn't expect a similar bounce for him even if he were to receive more attention.
EDIT: You know all the crap you hear the pundits spewing about how "Congress is deeply unpopular so the Democrats could be in trouble"? When tehy bother to break it down, Democrats in congress fare far better than Republicans in congress. In addition, there's this poll:
NYT/CBS poll, yesterday
In general, is your opinion of the Republican Party favorable or not favorable?
Favorable - 37%/Not Favorable - 54%
In general, is your opinion of the Democratic Party favorable or not favorable?
Favorable - 52%/Not Favorable - 38%