Peterborough, New Hampshire (CNN) - New Hampshire U.S. Sen. Kelly Ayotte, in an e-mail announcing her endorsement, emphasized Mitt Romney's strength in a potential general election match-up against Barack Obama.
Ayotte will officially endorse Romney on Sunday afternoon. The former Massachusetts governor was the "strongest candidate" in the GOP field to take on Obama next year, she wrote supporters.
"Mitt Romney has proven not only through his prior experience as a successful businessman and governor, but also through his solid campaign and excellent debate performances, that he is that candidate," she said.
Ayotte is a popular first-term senator and her support has been highly coveted.
A former state attorney general, Ayotte voted against the debt deal hammered out in Congress this summer and is seen as a strong conservative on issues of finance and defense.
Earlier this year, she introduced a bill to mandate accused terror suspects be tried in military courts.
In the e-mail, Ayotte said she believed Romney would keep the country safe "in a dangerous world."
"He will remain vigilant in the fight against al Qaeda and Islamist terrorists, and his national security decisions will be based on advice from our military commanders – not political polls," she said. "With a rising China and persistent nuclear threats from rogue nations, we need Governor Romney's strong, steady leadership to vigorously protect American interests."
Her support for Romney will follow that of other prominent state Republicans, including former Gov. John Sununu and former U.S. Sen. Judd Gregg.
Ayotte will endorse Romney at his 2:30 p.m. ET rally in Nashua, said the New Hampshire Union Leader, which was first to report the story.