NASHUA, N.H. — Mitt Romney's Republican presidential campaign steamed forward this weekend, scoring one of New Hampshire's most significant political endorsements and fueling a growing sense of inevitability surrounding the former Massachusetts governor's White House bid.
A beaming Mr. Romney stood shoulder to shoulder with Sen. Kelly Ayotte of New Hampshire on Sunday afternoon, several hours after the popular Republican senator's decision became public.
"There's one person in this field who is prepared to lead the United States of America and that is Mitt Romney," Mrs. Ayotte told cheering supporters gathered on the City Hall steps. "Most importantly, there is one person who I know will ensure that Barack Obama is a one-term president and that is Mitt Romney."
The freshman senator is the latest high-profile addition to an organization that already included Granite State Republican heavyweights like former Sen. Judd Gregg and former Gov. John H. Sununu.
But even in a world where the impact of endorsements is often exaggerated, Mrs. Ayotte's public support is a significant step forward for Mr. Romney in New Hampshire. It's led prominent Republicans to suggest that Mr. Romney - who already enjoys tremendous advantages in the first-in-the-nation primary state - has become so strong here that the real contest on Jan. 10 will be for second place.
"It's certainly going to push him even further ahead. I think this is a very big deal," said Jennifer Horn, a leading Granite State conservative who isn't affiliated with any campaign. "I think it would take something fairly cataclysmic for someone else to come in first in New Hampshire at this point."
Republican operatives here note that Mrs. Ayotte is perhaps the most popular politician in the state, having won a resounding victory just one year ago. She brings a network of roughly 3,000 volunteers and 7,000 donors, according to Steve Duprey, a New Hampshire member of the Republican National Committee.
Like New Jersey Gov. Chris Christie's endorsement earlier in the fall, Mrs. Ayotte's support also offers a bridge to more conservative voters, who have been reluctant to endorse a candidate with a mixed history on social issues.
Mr. Romney has struggled to win over that voting bloc in New Hampshire and elsewhere, although some have begun to reluctantly embrace his candidacy in light of repeated stumbles by his rivals.
"Kelly is not an ivory tower establishment-type elected official," Ms. Horn said. "She brings a tremendous amount of credibility among grass-roots conservative votes."