Let's look at this rationally, and examine the positions advanced by the Clinton camp to explain why their candidate is superior when it comes to running against a Republican and will make a better president.

1. Obama is not fully vetted - this is the classic political game of taking your worst liability and turning it into a supposed strength.  There are dozens of scandals that have managed to variously ensnare the Clintons over the years; any and all of them are fair game in the general.  Small groups of kooks will be enshrined and given the veneer of authenticity -- fake grassroots organizations with web sites, and "concerned citizen" surrogates on YouTube, blog plants, all covered by national press and brought to youby the same people who cooked up Swift Boat Vets for Truth.  That too was an old story, and thoroughly debunked, but was resuscitated and vomited up for the voting public with "new and improved" facts.  You think that McCain, using ex-Bush campaign staff, can't or won't find people to put a new spin on an old story?  New stories are easier for the candidate to dismiss and frequently fail to gain traction - the Bush DUI and story did not torpedo his chances at being elected and the cocaine use story disappeared after the thinnest dismissal.  It's all about how the dirt fits into the narrative of the moment, irrespective of its vintage, and the hachet men for the GOP are better storytellers than those working for the DNC or any Democratic campaign.  With a limited number of fronts on which to assert control of the media cycle, Obama has an edge compared to Clinton, who will have to defend heself against not only the gammut of recycled attacks, but also against newly-minted issues, like Bill's trip to Kazakhstan.  It also doesn't hurt that most of the purported Obama dirt revolves around adherence to religion and association with religious figures.  I think questioning faith is a gigantic turn-off for most voters that the GOP would want to target and any attempt to create a de novo lunatic fringe based on the Muslim allegation will be pathetically transparent.

2. Hillary's wins in big states portend greater strength in the general election - as has oft been cited, Clinton's support will largely become Obama's support if he is the nominee because the Clintons will be helping him to get elected.  The big states that Hillary has taken are pretty reliable in their tint on election night.  There is no particular benefit to "winning the crap out of NY" as opposed to "carrying NY."  A corollary to this is Clinton's reliable support among women, older voters and middle-income voters -- these will also flow to the eventual nominee.  While some demographic segments might be slightly more at risk (e.g., Latinos), there are certainly many ways that this can be addressed by smart campaigning that illustrates that votes for a Republican are votes against self-interest.

3. Obama's wins in red states don't matter because he won't win them in the general - against McCain, Obama draws greater support from Independents and moderates.  The far left and youth vote will not turn out in the same numbers for Clinton as for Obama, and the stalwart conservatives will stay home in higher numbers in a McCain / Obama race (see next).  Clinton supporters seem to be to be perpetual victims of conventional wisdom, navigating the car using only the rear-view mirror and the reassurances of the radio announcer.  If you think bloodsport for the middle is the only possible outcome for this race, then you're asking for a future president Clinton to govern on a mandate that's just as narrow as that we have enjoyed for well over a decade.  That's no way to recruit partners for the advancement of this country and its people if your election is the bitter fruit of an acrimonious 51/49 cage match.  That script ends with tragi-comic paroxysms of failed legislation and wasted detente followed swiftly by heavy Dem losses in both houses of Congress.  To avoid this, a ticket with appeal to a broader demographic and political spectrum is an absolute requirement.

4. Republicans fear running against Clinton - if you've been listening to AM radio at all over the past eight years, you've been treated to the "Socialist Hillary" schtick pretty regularly.  She's a very popular  -- and profitable --punching bag for the right, and she will amplify arch-conservative turnout in any election that features a Republican.  This is electoral college gold for McCain, who will be unable to close the sale with conservatives despite the laughable backpedalling by the likes of Limbaugh, Hannity, and Coulter in recent days.  The Venn diagram of the spontaneous voter support for McCain and Clinton has a lot of overlap, and higher conservative turnout could easily tip the balance, much as we saw in '04, when they actually liked the candidate.  The AM dial has been featuring increasing amounts of anti-Obama rhetoric since Tuesday -- wonder why the Dittoheads and Hannitards might want to handicap him now?

5. Lacks the "Co-president Bill" / "Her own presidency" dichotomy - Hillary likes to cut this both ways, relying on Bill's record in the '90s to bolster her own resume, while distancing herself whenever the discussion wanders too close to some (perceived) negative involving Bill personally or politically.  She's been deft at parrying most observations on this contradiction, but she won't be able to squirm free of this double standard in debates with McCain.  We've all been reminded that Bill only won with voter support in the mid / upper 40s, and this provides no assurances that the same machine will be able to prevail without a third candidate to dilute the Republican vote.

6. Not "ready on day one" - look, every president elect spends November to January assembling staff and being briefed by pertinent officials.  Much will have changed since 2001, except the shredders in the Justice Dept. and Pentagon will likely be burned out from overuse next January.  Nobody's ready on day one to resolve a war except someone who's done it before and nobody will traipse into the oval office and immediately transmit a universal health care plan to Congress and see it pass the same day.  As much as she might "be her own president,"  Hillary would spend the early days learning who that president is and how to be effective in that role and capitalize on working relationships.  It would be the same for BHO.  Any assertion to the contrary is entirely reliant on #5 above, and therefore a fallacy.  Recent events further underscore the open question regarding relative competency in the present tense: is she ready to campaign on month twelve?

7. Obama, the "empty vessel" - for some reason, lack of access to the national Democratic apparatus precludes the possibility of "accomplishing" anything, or so Clinton surrogates would have me believe.  Try this: minority youth from broken home puts self through college and law school, becomes civil rights attorney and community organizer along the way.  Do we "handicap" Clinton for being handed a Wellesley education or for becoming a corporate lawyer?  Obama resonates with people because his experience aligns better with that of average Americans and their hopes for the future.  For me personally, the guy who just finished paying off his student loans has much more in common with me than the guy who tosses $5M into the campaign kitty without batting an eye.  Hillary constantly reassures us that she will "wake up every morning" thinking about our problems, and these protests do little more than convince me that these concerns are not native residents in her thinking.  Obama does not suffer from an empathy deficit that must be actively exorcised and that's why he connects with people; not because of some pretty prose delivered trippingly off the tongue.

8. Hillary knows best how to win against the Republicans - this is the whopper of the bunch.  The former first lady has run an unsuccessful campaign to date.  With the advantages the started the race with, there is simply no reason to believe that her campaign leadership are up to snuff.  You don't run out of money and give up the majority of pledged delegates to a virtual unknown when you start out as the default nominee and supposedly magnificent establishment bona fides.  This against a candidate who -- let's be honest -- isn't even really attacking her in any manner resembling what will happen after the convention.  I hear a lot of grousing from Clinton supporters regarding media coverage and the supposedly exalted status of Obama in the press.  How is that not a valid metric of success?  If the Clinton campaign cannot redirect the narrative of the news media to suit the interests of its candidate -- apart from insisting that reporters who make reprehensible statements be fired -- than what good is it doing her and how will it help her to succeed in the general election, which will doubtless be covered by the same "biased" (notice how the hated Republican mantra has found its way out of losing Republican politics and into losing Dem politics) MSM?  Overall this points to poor and failed execution on the part of her staff -- that might hold the field in Senate races against ho-hum candidates in a cherry-picked Democratic-leaning state, but it's no sure bet to win the White House.

So what should happen?  The Clinton camp should acknowledge that it would be a drag on any ticket.  Obama should bolster his position with a diplomatic technocrat to narrow his vulnerability to attack based on experience.  Richardson seems to be a good fit in that regard, IMO, but I don't know if that would poll substantially better than Obama / Clinton.