MANCHESTER, N.H. — Cory Booker is returning to the first-in-the-nation primary state for a trip that could turn out to be a tuneup for the New Jersey senator’s potential Democratic presidential campaign. Booker’s been invited by the New Hampshire Democratic Party to headline their post-midterm election “Victory Celebration” Saturday in Manchester. He’ll also be the main attraction at house parties in Concord, Nashua, and Keene. Booker’s said repeatedly in recent weeks that he’ll take the holiday season to assess whether he launches a White House campaign. The visit is Booker’s second to New Hampshire in two months. He campaigned with now-Congressman-elect Chris Pappas and gubernatorial nominee Molly Kelly at a rally at the University of New Hampshire, and with Congresswoman Annie Kuster at Dartmouth College in late October, shortly before the midterm elections.