A central claim of Obama and his cheering squad is that he would be the stronger general election candidate than Hillary because he would be more attractive to Independents and Republicans than she would be, and that elections are decided on the margins. The unspoken part of the claim is that all Democrats would vote for him without question.
It wasn't a bad argument, per se, and there was some plausibility to it. Independent voters are a notoriously fickle lot, prizing their faux "independence" above political effectiveness and noted more for impulse voting than for supporting a consistent platform. For every Obamacan you can find a Paultard. They don't tend to go for conventional candidates - witness the Independent vote for Ralph Nader over Al Gore. Given that Republicans are the party of racist bigots (Read your Krugman), it was not very palusible that he would draw a significant enough number of Republicans to have an electoral impact. I also thought Clinton was far more popular with the Democratic loyalists than anyone gave her credit for. A Gallup poll back in November (sorry, can't find link) showed that Hillary had a larger group of fully committed supporters than any other candidate. Even so, there were some persuasive points to the claim because of the apepal to Independents.
What was clear from the start of the Obama campaign was that he took the Democratic base for granted. He did not think there could be any defections from it that would make a difference, and so he hasn't spent much time asking for thier support. He has been courting not just weird left-leaning Independents, but aggressively going after right-leaners and Republicans. He has signaled that he won't push for universal health care, that he's willing to revisit Social Security and open it up for changes, that he will have Republicans as cabinet members and senior advisors. He is even refusing to count Florida votes as a way to prevent losing a tenuous lead among delegates. (Ahem...) Amid all the racism calumny thrown at Hillary, it's easy to forget the blatent sucking up to the rightwing in his Reno newspaper interview, bashing Bill Clinton, praising the Republicans as the party of ideas, and admiring Reagan. It is this behavior that makes regular Democrats feel taken for granted if not simply disdained. Whoever is the nominee gets the spoils, as it is assumed even today, so the trick was to pack the primaries with non-Democrats who were recruited to vote against Hillary.
The Democrat for a Day promotion really showed the true face of the Obama campaign. It began in Florida, explicitly trying to bring people in to vote against HRC, but to leverage their CDS in Obama's favor. It became significantly more crude in Nevada, where people were told to change party registration specifically to vote against Hillary. This brought about a backlash, but the measure has continued wherever there was a closed primary. It is being run in Pennsylvania right now, and it is clearly aimed at getting Republicans to cross over and vote their CDS. The key in all of this is the assurance that the party-switcher can easily go back to being a Republican, Liberatarian, Independent, etc., the minute the primary is over. These people were never intended to remain Democrats - they were Obamacans, unconnected to our party.
Party building is not done by gaming elections for a particular candidate (though gaming elections is something parties need to know how to do), it is about increasing voter identity with a party, because the party is what enables policies and programs to be enacted over time. Individuals do not manage governments, parties do, and the chilling effectiveness of the Republicans is due to the party apparatus that supports the candidates. The most simple, long lasting way to build party identification is by presenting and then delivering upon something the voter sees as being in their self-interest. This can be something as reprehensible as segregation, which moved millions of southern whites into the Republican column, or something as empowering as FDR's New Deal, which moved millions of AA's from "the party of Lincoln" to the Democrats.
The recent Gallup poll that is giving the Blogger Boyz the vapors over those evil, back-stabbing Hillary supporters actually puts to rest Obama's claim to be the stronger candidate in the general election. While people are framing this information as showing that HRC's supporters are "more divisive", what it actually shows is that voters of all kinds are more satisfied with HRC as the Democratic nominee than they are with Obama - including AA voters. If Hillary is the nominee more people will vote Democratic, including more Independents.
Contrary to the frothing, CDS-afflicted pundits, Hillary holds on to the constituencies most prone to defection within the Democratic Party (Regan Democrats, male voters) better than Obama and she will retain a higher number of Independents. These are the largest parts of the Demoratic electorate. While I have no doubt there are a non-trivial number of Obama supporters who will not vote for Hillary, especially after the pounding alleged leftists have been giving her, she starts by retaining larger portions of the parts of his constituencies likely to vote Democratic (and thus whose defections would erase possible gains among Independents), which means she has less ground to make up among Democrats themselves.
When this factored into the clear advantage she enjoys over him with states that can deliver the electoral votes, the general election argument no longer holds any water. The reason she does this is because she is running as a Democrat on every day, not simply an opportunist looking for a way to fiangle his way to a questionable nomination. Her devotion to the party, her willingness to fight for it just as strongly as she fights for herself, is what gives her supporters confidence that she in unafraid to take on the tough battles for us - universal health care, shoring up the economy, restoring the honor of our nation around the world, protecting civil liberties, and improving the lives of ordinary people.
Who knows? If Obama had not been so eager to fellate the corpse of Regan in exchange for a few cross-over primary votes, maybe Democrats would be more inclined to give him their votes in the general.