N.H. Rev. Stat. § 653:9
The presidential primary election shall be held on the second Tuesday in March or on a date selected by the secretary of state which is 7 days or more immediately preceding the date on which any other state shall hold a similar election, whichever is earlier, of each year when a president of the United States is to be elected or the year previous. Said primary shall be held in connection with the regular March town meeting or election or, if held on any other day, at a special election called by the secretary of state for that purpose. The purpose of this section is to protect the tradition of the New Hampshire first-in-the-nation presidential primary.
RSA 653:9
1979, 436:1. 1995, 289:1. 1999, 161:2. 2007, 212:4. 2010, 121:1, eff. Aug. 8, 2010.