ABOUT THAT FOX NEWS POLL…. There have been some national polls showing John McCain narrowing the gap a bit this week — which is not at all unexpected — but Fox News raised some eyebrows this afternoon with a new poll showing Obama’s lead down to just three points nationwide, 47% to 44%.

A week ago, a similar Fox News poll showed Obama’s lead at nine points, 49% to 40%, which certainly gives the appearance of some favorable movement in McCain’s direction.

But it is Fox News, which, as a rule, is grounds for some skepticism. In this case, the results are worth a closer look.

One of Marc Ambinder’s readers noted that Fox News changed its sampling for this poll, as compared to last week’s. Seven days ago, 43% of respondents were Dems, and 37% were Republicans. This week, 41% were Dems, and 39% were Republicans. Fewer Dems and more Republicans will obviously produce a more McCain-friendly result.

So, why change the weighting in the poll? Ambinder asked Pollster.com’s Mark Blumenthal for his take.

He tells me: “If they have been weighting by party, and they suddenly changed their weighting, I’d say it’s a pretty questionable practice. The last four Fox surveys all varied slightly in terms of party ID, so I’m not sure that’s what they’ve done. That said, if the other surveys this week show no similar ‘shift’ in party, then it’s probably reasonable to discount this result.”

Steve M. had a good item on this, noting, “Democrats had a six-point party-affiliation advantage in the last poll. Now it’s two? Anybody think that in any way jibes with reality right now? According to Gallup, that’s less than the Dems’ party advantage in 2006 or 2004. Anyone think they’ve slipped over the past two years? Preposterous. But it got Murdoch just the number he wanted.”

Something to keep in mind when Sean Hannity and Bill O’Reilly trumpet this poll tonight.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.