In an interview with Fox News Channel's Sean Hannity set to air Monday evening, Romney says the spot will remind Granite State voters of the promises Obama made to them as a candidate.
"The contrast between what he said and what he did is so stark, people will recognize we really do need to have someone new lead this country," Romney said, according to excerpts released by the network.
Romney has spent the last three days in the nation's first primary state, announcing endorsements from two of the state's top elected Republicans -- Sen. Kelly Ayotte and Rep. Charlie Bass.
Polls have long shown Romney to be the frontrunner in New Hampshire, though the gap appears to be narrowing with just 50 days until the state's primary. Still, the ad shows Romney is keeping his focus on a potential general election matchup with Obama rather than engaging directly with Republican rivals.
Romney told Hannity that he is simply returning fire; the Romney campaign says Obama and his campaign team have an "obsession" with the Republican.
"One of his advisors said their strategy will be to kill Romney," the presidential hopeful said. "He can't talk about his record and get reelected. So what he'll do is try and assassinate, on a character basis, his opponents and his opposition. I'm hoping that's me, but I'm not looking forward to those attacks."
New Hampshire is "critical" to his campaign, Romney said, but he'll also "campaign aggressively" in the other early states.
"New Hampshire shouts when it comes to deciding who our nominee will be," he said. "I want to win here in -- in New Hampshire. Heck, I'd like to win everywhere. ... I want to get the nomination. I'm going to do what it takes to get the nomination."
The White House said Monday that Obama will meet with a New Hampshire family during his trip to Manchester, and urge Congress to extend the payroll tax holiday.
Obama's last event in New Hampshire was in February of 2010, when he was pitching his healthcare reform plan. He has since spent considerably more time in other, more electorally rich general election battlegrounds.
A Bloomberg News poll released last week showed Romney leading Obama 50% to 40% in a hypothetical general election matchup in New Hampshire.