- failure to anticipate that the Fox News Channel, on which Newt overrelied, would double-cross him
- failure to qualify for the ballot in Virginia which generated enormous doubts about the viability of his campaign
- statement that Newt would not vote for Ron Paul if he won the Republican nomination, unnecessarily alienating many Republicans whom Newt might have been able to persuade to support him
- overspending in an unsuccessful effort to compete in Florida, where the elderly voters were going to be influenced by the pro-Mitt Romney Fox News Channel
- poor response to Ron Paul's accusation that Gingrich is a "chicken hawk" - Gingrich should have emphasized that he opposes a draft and military service today is not compulsory; would Ron Paul oppose calling the police if he had not been a policeman himself?
- inability to point out how Rick Santorum was merely a stalking horse for Mitt Romney
- inability to make abortion a leading issue in the campaign, compounded by his failure in the 1990s to champion the issue by (for example) addressing the March for Life as Speaker of the House (which Newt never did)
(please add to list)