In several interviews, aides to Mr. Obama said they were impressed with the early campaign tactics of Mr. Romney and Mr. Pawlenty. They said Mr. Romney had been wise to remain out of the fray for as long as possible — giving rivals less time to attack him — and Mr. Pawlenty wise to barnstorm important states, early, to become better known. Mr. Romney’s previous experience as a candidate, they suggested, could help him deal with the problems he faces. They said they viewed former Gov. Jon M. Huntsman Jr. of Utah, until a few weeks ago Mr. Obama’s ambassador...