Mitt Romney marked his arrival in New Hampshire on Wednesday with an endorsement by Senator John McCain, one of the state’s favorite adopted sons. The endorsement came a day after Mr. Romney won the Iowa caucuses by a mere eight votes and helped Mr. Romney consolidate his support among the Republican establishment.

“New Hampshire is the state that will catapult him onto victory in a very short period of time,” Mr. McCain declared to applause at a rally here. Mr. McCain, who was the party’s nominee in 2008, gave a fiery speech against President Obama in what sounded like a reprise of that campaign.