Republican presidential candidate, former Governor Mitt Romney, speaks at the Values Voter Summit in Washington. (Manuel Balce Ceneta/AP)

Romney’s campaign has snagged three big endorsements from former senator Judd Gregg, a popular New Hampshire Republican who will introduce Romney at his three campaign stops in the state on Monday.

Gregg served four terms in the U.S. House and two terms as governor before becoming a U.S. senator, a position he held until retiring earlier this year. One of New Hampshire’s most prized Republican endorsers, Gregg also backed Romney when he ran for president in 2008.

Romney also won the backing of former Florida senator Mel Martinez, who will chair Romney’s National Advisory Council. During the George W. Bush administration, Martinez served as Republican National Committee chairman and Housing and Urban Development secretary. A Cuban-American, Martinez was one of the GOP’s most prominent Latino officials. His and then-Gov. Charlie Crist’s January 2008 endorsements of John McCain are credited with helping McCain win the Florida primary and clinch the presidential nomination.

Also Monday, Romney announced the endorsement of Rep. Michael Grimm (R-N.Y.), a freshman House member who is aligned with the tea party. Grimm is one of the first members of the House’s class of 2010 to endorsed a presidential candidate. Grimm is an ally of former New York mayor Rudy Giuliani (R).