New Hampshire Sen. Kelly AyotteKelly Ann AyotteErnst, Fischer to square off for leadership post The Hill's Morning Report: Koch Network re-evaluating midterm strategy amid frustrations with GOP Audit finds US Defense Department wasted hundreds of millions of taxpayer dollars MORE will endorse GOP candidate Mitt Romney for president.

The New Hampshire Union Leader reports Ayotte will join Romney, the former Massachusetts, governor at a campaign rally in Nashua on Sunday. Ayotte will also be named co-chairman of Romney's national advisory committee.

In an interview with the Union Leader, Ayotte said Romney had "proven through his experience as a successful businessman and as an effective governor and his excellent debate performances that he is best prepared to lead our country and also, very importantly, to make sure that Barack ObamaBarack Hussein ObamaObama: Are we a nation that rips families apart? Another chance to seek the return of fiscal sanity to the halls of Congress Colombia’s new leader has a tough road ahead, and Obama holdovers aren't helping MORE is a one-term President."

She added that Romney would "get America back to work and get our fiscal house in order."

Ayotte's endorsement holds great weight in the Granite State. A first-term senator, she previously served as New Hampshire's attorney general.

In a statement, Romney thanked Ayotte for her support. "I am honored to have her support and look forward to working with her to put an end to Washington’s spending addiction so that our children and grandchildren will not be burdened by irresponsible policies and endless debt,” said Romney.

Last month, Romney gained the endorsement of former New Hampshire Gov. John Sununu (R). Republican Reps. Frank Guinta and Charlie Bass have yet to endorse a candidate in the GOP primary.

A recent Bloomberg News poll shows Romney leading Obama by 10 percentage points in New Hampshire, 50 percent to 40. The president won the state in 2008.

The Bloomberg poll also finds Romney holding a commanding lead among his GOP rivals. Romney leads the pack with 40 percent, followed by Ron Paul at 17 percent and Newt Gingrich with 11 percent.

This story was updated at 1:29 p.m.