In a call last Sunday morning, just hours after Mr. Romney’s double-digit loss to Mr. Gingrich in the South Carolina primary, the Romney team outlined the new approach to the candidate. Put aside the more acute focus on President Obama and narrow in on Mr. Gingrich.

Find lines of attack that could goad Mr. Gingrich into angry responses and rally mainstream Republicans. Swarm Gingrich campaign events to rattle him. Have Mr. Romney drop his above-the-fray persona and carry the fight directly to his opponent, especially in two critical debates scheduled for the week…

By this weekend, Mr. Romney’s aides were on the offensive and increasingly confident, with some combination of their strategy and Mr. Gingrich’s own performance swinging polls in Mr. Romney’s direction. Even as it acknowledged the damage inflicted on Mr. Romney by the past several weeks, his team suggested that it had learned a lesson about never letting up on rivals, especially if Mr. Romney wins the nomination and confronts Mr. Obama in the general election…

If Mr. Romney does win here on Tuesday, it will have been through a blistering and unrelenting series of attacks.