For that matter there certainly is no guarantee that Obama would nominate moderate to liberal judges.  The Roberts confirmation story is IMO the Rosetta Stone to Barrack Obama. His Unity schtick it appears is more than just schtick.  How do we know his White House staff will not be larded with Republicans? How do we know he won't leave some Republican appointees in federal agencies? Anyone who maintains that he'll bring the other side to the table as a starting point simply can't be trusted. This is especially ironic when Democratic Party power is increasing. Increased power is an opportunity to ram through desperately needed reforms so what in hell is the Democratic Party doing by nominating someone who would through away that opportunity.
There are many problems that will not be solved with compromising legislation, legislation that may have no impact. It's certainly happened before, the appearance of action but lacking substance. Obama's US Senate record yields evidence that he's willing to act in that manner.

Since Roosevelt the Democratic Party has promoted government activism to tackle the nation's problems.  Obama's dependence on the Chicago school of thought would move the Democratic Party away from that role. That's what the 'change' is all about.

When Obama unnecessarily put Social Security back on the table it should have sent alarm bells ringing. He looked like a Trojan Horse candidate.  I don't believe he's a Trojan Horse but he's put a critical program at risk and it doesn't help that one of his principle policy advisors is a known friend of privatization.  When Bush made his privatization threat, Democrats in Congress pulled together to insure that Bush's foot stayed firmly on the third rail.  That's probably the only reason they made a unified stand. I have a chilling feeling that at least some Democrats in Congress aren't wedded to insuring that Social Security remain a robust public only program. So what happens if a Democratic President decides to "solve" the Social Security "crisis" by proposing some Rube  Goldberg "remedy?"

I could go on and on about the potential damage. There are deeply serious character flaws in this man.  Through his actions he clearly exhibits traits that I personally loathe.

It really comes down to the future. I think about my little grandchildren, I don't want a schmuck President with a Democratic Party label. I don't want a Democratic Party changed to the extent that American politics is 'Mexicanized,' leaving only a choice between right and farther right.

I would add that partisans of both sides have been insulting and insufferable to their opposing partisans. However, the candidates to their credit, have behaved reasonably responsibly. I cannot ascribe the worst words of a Hillary partisan to Hillary or the worst words of an Obama supporter to Obama.

Whatever you think of Obama's short comings, Hillary Clinton wold be the first to tell you that sitting out or voting Mccain would be a serious mistake.