I think Kos makes a few good points on the lessons for the results last night in his front page post in the wee hours of the morning (at least on the east coast), and his thoughts certainly shouldn't be discounted. But I think there is more to it than just what kos said.
To be sure, Creigh Deeds severely damaged himself by trying to be McDonnell-lite near the end of the campaign, especially by saying he would consider opting-out of the public option. However, there was merely the final straw for many Democrats in a pathetically run campaign in which his fate had already been sealed.
I think in this respect, kos is right in that Democrats need to run, at least marginally, like Democrats in races.
However, where he misses something is that Democrats don't have to necessarily run as strong progressive candidates to win, especially in states like Virginia. Sure, Obama won Virginia. But also look at the last 4 major elections state-wide other than that: Warner for Governor, Kaine for Governor, Webb for Senate, and Warner for Senate. None of these candidates ran on a particularly progressive platform and all largely ran moderate or centrist campaigns.
I think this shows that democrats who run as moderates and centrists can still be very successful, especially in places like Virginia.
The primary difference I saw between Deeds and the above four candidates is that Deeds ran a befuddled and confused campaign, where he didn't seem to know where he stood, and thus, just didn't look like a strong candidate.
Meanwhile, while it may be sad, McDonnell put out the impression that he knew what he was doing, knew what he wanted, and had the strength to execute it. Now, whether he'll actually be the governor that most of the people who voted for him expect him to be is obviously yet to be seen, but next to Deeds, it was hard to see McDonnell as anything but a shining beacon of strength.
And this is where I think the primary lesson is: while not pissing off the base is a good place to start in an election, it is perhaps even more important that you come up with a plan, and you stick to it. People might not vote for you, even if you are a strong looking candidate, but people definitely won't vote for you if you don't look like a strong candidate, and that was Deeds' primary failure.
His pushing away of the left, especially at the end of the campaign (only to realize his mistake and invite Obama in at the last moment) was merely a result of an already flailing campaign, caused by Deeds lack of focus and policies. The slap in the face to the base just made the margin all the more worse, but it didn't change the outcome of the race. Deeds was already doomed by that point anyway.
Part of the problem with criticizing Deeds on his policies is, frankly, I'm not totally sure what they were. I'm not sure anyone really knew, and that is the entire problem. It's not that he had policies that Democrats, or the people at large disagreed with - it's that people had no idea what his policies even were to begin with. And as the saying goes, "better the devil you know..."
Of course one complicating factor in Virginia is the bad economy, which I think lent people to want a change in the governor's mansion anyway, plus Virginia's tradition of electing a governor of the opposite party of the President, but there were factors that could have been overcome.
I disagree with kos' apparent suggestion that, had Deeds only run as a strong progressive, then he would have won! I don't think that was necessary. The biggest thing Deeds could have done was actually run a strong and focused campaign, regardless of what the campaign was about. As long as he wasn't too intolerable to the base, they still would have come out to vote for him instead of McDonnell, as they have done before.