Be skeptical about latest batch of swing state polls

Three new NBC/Wall Street Journal/Marist polls show Barack Obama winning Ohio, Florida, and Virginia --- and winning them handily.

In fact, so handily that all of them need asterisks and some big caveats.

I've been noticing over the months that this polling group's surveys tend to produce outliers in state-by-state polling, but didn't realize just how dramatically until I looked into it.

Obama has led in every NBC/WSJ/Marist survey of these three states this year, and his current leads aren't even as big as some the group captured earlier this year -- for example, he once led by 17% in Virginia and by 12% in Ohio!

So it's hard to buy the spin that these polls represent some massive shift in the race.

Here are the current Obama leads, according to NBC/WSJ/Marist:

OHIO: Obama 50% Romney 43%

VIRGINIA: Obama 49% Romney 44%

FLORIDA: Obama 49% Romney 44%

Now, let's compare that to the group's previous polls of those states...

NBC/WSJ/Marist have released only two previous polls of Ohio this year -- one had Obama up 6%; the other had him up 12%.

The polling group has released only two previous polls of Virginia this year -- one had Obama up 4% and the other had him up 17%

And finally, the polling group has released two previous polls of Florida this year-- one had Obama up 4% and the other had him up 8%.

So on the basis of that, it's pretty safe to say that NBC/WSJ/Marist has been delivering polls of theses states that (for whatever reason) tend to be outliers this cycle -- sometimes dramatically so.

And even this batch of new polls seems to be outliers.

To wit: In the RCP average of Virginia polls, Obama has a .4% lead. In this poll, he's got a 5% lead.

In the RCP average of Florida polls, Obama has a 1.3% lead. In this poll, he's got a 5% lead.

In the RCP average of Ohio polls, Obama has a 4.2% lead. In this poll, he's got a 7% lead.

So Obama's lead in NBC/Marist surveys is between 3%-5% larger than the RCP average for those respective states.

CONCLUSION: In reality, Obama is probably leading in two of three states (Ohio and Virginia), and is just behind in the other (Florida).

Make no mistake -- he's doing well, and has the electoral college advantage right now.

But past evidence suggests the real result is much, much closer than those delivered in NBC/WSJ polls.

I updated this post.