(Updated below)

We leave you this holiday eve with two big political mysteries: Will Scott McClellan come clean about the role George W. Bush and Dick Cheney played in the outing of CIA officer Valerie Plame and its coverup, and is the Obama surge in Iowa real? Some of us will be working this weekend to try to bring you answers.

On McClellan, I've been frankly stunned by the lack of coverage in big media, particularly the New York Times and the Washington Post, which left the story to the Associated Press and Reuters on their Web sites. Joe Conason breaks it all down in an excellent column today. The only thing I have to add is that McClellan's insistence that Bush didn't lie, in a statement by his publisher Peter Osnos, makes it even more crucial that Congress continue to persevere to get to the bottom of the story. Apparently McClellan now says he's not claiming Bush knowingly passed along false information about the role of Karl Rove and Scooter Libby in outing Plame to reporters. He's just saying Bush was "involved" in McClellan's passing along false information. Unknowingly. Or something. Thanks, Scottie.

On Obama, I've been surprised that Oprah's decision to campaign for him is being treated as big news. It didn't strike me as surprising -- she endorsed him months ago, why wouldn't she campaign? We know Oprah can sell books; what we don't know is whether she can sell candidates. I've heard it said Oprah might help him cut into Clinton's lead with black voters, particularly black women voters (in an October CNN poll, they favored Hillary roughly 4-1 over Obama or Edwards.)

But I think Oprah will be far less important to black voters than the strength of Obama's overall campaign, and whether his recent surge in Iowa persists. African-American voters tend not to do protest votes; they know politics matters. Clinton is currently leading among black voters, and in endorsements by the Congressional Black Caucus as well (14-12, with three members supporting John Edwards), both because they know where Clinton stands on the issues, and because she's run the most convincing campaign to date. Oprah can't change that, but Obama can, by building on the last week's momentum. If you haven't read them already, check out Walter Shapiro's interviews with Obama and Sen. Joe Biden, as well as his overview on the Democrats' foreign policy debate. I would call the Clinton-Obama spat, over the importance of Obama's childhood years spent overseas, for Obama. Clinton looked a little petty seeming to deride him for what he did as a 10-year-old, opening the door to Maureen Dowd's nasty column today, noting that Hillary Clinton wasn't exactly treasury secretary when her husband was in the White House.

I'll be on MSNBC's "Hardball with Chris Matthews" tonight (7 pm ET/ 4 pm PT) and on CNN's "Reliable Sources" on Sunday (10 a.m. ET/7 a.m. PT) to discuss both stories. And I'll be checking in over the weekend. Happy Thanksgiving!

Update: Two noteworthy points from "Hardball," which will repeat shortly: Chris Matthews did his own reporting, which I admire, and got Peter Osnos to say that while McClellan insists Bush and chief of staff Andrew Card didn't knowingly lie about Plamegate, readers are going to have to make up their own minds about that question when it comes to Dick Cheney. So McClellan, so quick to exonerate Bush, leaves Cheney twisting slowly in the wind. Fascinating. Later in the show, when Matthews and I had an interesting and contentious back and forth about whether to believe Iowa polls showing Clinton trailing Obama among women, I cited Iowa's election of a female lieutenant governor, Sally Pedersen, as evidence Iowa will support strong women candidates. And I was very proud to pull that fact out of my overtaxed, pre-holiday brain on "Hardball." In fact, Iowa's current lieutenant governor isn't Pedersen, who left office in 2006, but Patty Judge, who succeeded her. I was right about the larger point -- Iowa elects women! -- but I regret being wrong about Judge.