Mitt Romney waited until the presidential debates in the final five weeks of the election campaign to make his long-anticipated shift to the political center after previously espousing strongly conservative stances to win the Republican nomination.

The move appeared to catch President Barack Obama by surprise at their first face-to-face match up. His lackluster performance against a strong showing by Romney helped the former Massachusetts governor to catch, and in some places, pass the president in the polls.

The roller-coaster ride of the 2012 campaign has been particularly volatile because of the more than two dozen debates dating back to last year, including three presidential showdowns...