Across the party’s campaigns, committees and super PACs, internal polling gave an overly optimistic read on the electorate. The Romney campaign entered the last week of the election convinced that Colorado, Florida and Virginia were all but won, that the race in Ohio was neck and neck and that the Republican nominee had a legitimate shot in Pennsylvania.

The National Republican Senatorial Committee consistently had a more upbeat assessment of races in North Dakota and Montana, among others, than their Democratic counterparts. One GOP poll even showed Indiana Senate candidate Richard Mourdock holding even with his opponent, even as public polls showed the embattled Republican hemorrhaging support. A Republican poll taken by Susquehanna Polling and Research showed Pennsylvania Senate candidate Tom Smith leading Democratic Sen. Bob Casey by 2 points a few weeks before the election; Casey won by 9 points…

“On the Republican side, this was the worst cycle ever for polling and there’s nothing that even comes close to it,” said GOP strategist Curt Anderson, who helms the media and polling firm OnMessage. “It was a colossal disaster and it wasn’t confined to the presidential campaign.”…

By assuming that only the most enthusiastic voters would actually show up, Republicans greatly overestimated their national position. Operatives and activists rejected public polling data that showed substantially more voters identifying themselves as Democrats in states like Ohio and Virginia, giving Republicans an unwarranted sense of confidence that crumbled last Tuesday.

Democratic pollster Jef Pollock said it was incomprehensible to him how strategists on the other side so dramatically missed the mark in so many races — especially, he said, since “many of the polls that were in the public domain were proven to be right.”