It's politics. In the US there has been a lack of inspiration lately. Inspiration meaning "sound bites". Kerry "endorsing" Obama does little to help the cause (being as Kerry is more or less an "also ran", not as bad as our Dion though).
When it come to todays democratic outlook it's not about conservative or liberal, democrat or republican. It's not really about ideals.
The majority of the voters are one of two parties: the lazy and the angry.
Lazy people will vote for the "safe choice".
Angry people will vote against the person who made them angry.
If you're the incumbant you want more lazy people than angry. Low voter turn-out won't hurt you if "lazy" is the mood.
Angry works depending on who made them angry. The Federal Liberal brand was punished because voters got angry. Likewise the Ontario Provincial Conservative brand was punished because voters got angry.
It's just the way things work. Everyone says they "look at the issues" but that really is far from the truth. They only look at sound bites (i.e. very singular issues). Package a sound bite well enough and you can either make or break an election.
Obama has done very well considering it was an uphill battle. As a strategist, I would leverage the chance to make a future sound bite of "History in the Making" by doing what I said above.
The reason for a short term for Hillary is because of her ego. Given too long she will mess things up bringing doom on her party. If I were a Democrat party strategizer the maximum I would give Hillary is two 3 year terms although I'd prefer a single 4 year term followed by a short 3 year first term with Obama then a second full term if things go well.
Of course there are certain aspects that can't be predicted completely (one bad sound bite and your dead).
Unless some big time miracle from "god" (i.e. vote fixing) happens, I can't see the Republicans winning the next term. Bush has done exactly what I thought he'd do. Even worst what is happening in Iraq and Afghan is exactly what I thought would happen (other than there being no WMDs).
In any case, the climate in the US right now is anger. IMO almost any candidate could run and win against the Republican party. By grooming for a Female President this run and a Black one next run, it's just too good an opportunity to pass up, especially with an angry voter base.
Even if it is just fluff, it doesn't matter because the voter base will buy it.