The Ace of Spades post suggests that Orca was a key reason for the defeat (though it doesn't explicitly assert it). The post attacks Orca and asks "If this had worked could it have closed the gap?"

Erick Erickson makes the suggestion more strongly. He points to the "Ace of Spades" post and uses it to reject the possibility that the election was a defeat for "conservatism". In http://www.redstate.com/2012/11/09/the-only-thing-you-need-t... he says that "the biggest problem the Republicans had on Tuesday night was not demographics, but turnout operations."

The post on Breitbart makes a similar suggestion and leads with "As Republicans try to explain their Election Day losses in terms of policy, tactics, and strategy, one factor is emerging as the essential difference between the Obama and Romney campaigns on November 6: the absolute failure of Romney’s get-out-the-vote effort, which underperformed even John McCain’s lackluster 2008 turnout. One culprit appears to be “Orca,” the Romney’s massive technology effort, which failed completely."

Orca is just the latest reason I've heard, previous theories (from staunch conservatives) can be best summarized by what I heard Charles Krauthammer say on Fox News (on election day). He dismissed the defeat by describing Romney as a "northeastern liberal".

[edit] See http://www.washingtonpost.com/blogs/election-2012/wp/2012/11... “I’m very surprised, as digital guy, about the pushback people are getting” over Orca, Moffatt said. “This didn’t materially change the course of the election.”