New Hampshire Republican John E. Sununu announced a campaign for U.S. Senate on Wednesday, hoping to reclaim a seat he lost nearly two decades ago and boosting the GOP’s chances of regaining a foothold in a region overwhelmingly represented by Democrats. Sununu, 61, is seeking the Republican nomination for the seat being vacated by U.S. Sen. Jeanne Shaheen, a Democrat who ousted him in 2008.