"Oh, how we all wish things had turned out differently!" Brown writes. He argues that Romney was 'right about so many things, whether the subject is the still-sputtering economy, an aggressive Russia moving to expand its sphere of influence, or the vacuum left in Iraq by the failure to leave behind a residual force to secure our hard-fought gains."
Romney, a former governor of Massachusetts, is well-known and very popular among New Hampshire Republicans. He won the 2012 primary there and owns a home in the state.
Brown is challenging Sen. Jeanne Shaheen (D-N.H.). A recent Suffolk University/Boston Herald poll showed Shaheen leading Brown by 10 points.
CNN first reported that Romney would endorse Brown.