I have been hearing this from a lot of Hillary supporters:
If Democrats are going to win the White House in November, they need a shotgun wedding in June. This is not something that either Barack Obama or Hillary Clinton wants to hear, nor is it anything party leaders have been willing to say — at least not publicly. But without both Clinton and Obama on the same ticket, Democrats stand a good chance of suffering a humiliating defeat in the general election.
As the mathmatics of the nomination become obvious to anyone not named Clinton, their will probably be a lot of calls for Hillary as VP. This would be an awful idea, she has supported the war with Iraq and seems to support war with Iran, just like John McCain. Picking Hillary as a running mate would signal that deep down Obama agrees with the hawks and would validate John McCains hundred year war strategy. In addition Hillary on the ticket would energize the conservative base(even though she is the most conservative candidate in the race right now, they still hate her).
Hillary Clinton is a less likeable Joe Lieberman at this point,having anywhere near the presidential campaign may help republicans but it does nothing for democrats trying to end the war in Iraq or end the Bush/Cheney depression.