From a press release.

New Hampshire Secretary of State David M. Scanlan reminds voters that the deadline to change one’s party affiliation before the New Hampshire State Primary Election is May 31, 2022.

Voters who wish to change their party affiliation should contact their local town or city clerk. Alternatively, voters can change their affiliation at any scheduled meeting of their local supervisors of the checklist. Voters who are unsure under which party they are registered can check their status on the Secretary of State’s Voter Information Lookup page at https://app.sos.nh.gov/voterinformation. If the voter information displayed on the Secretary of State website is incorrect, voters should contact their local supervisors of the checklist or clerk.

A voter who has not declared their party affiliation may vote in the State Primary; however, they must choose either a Republican or Democratic ballot on the day of the election. Once a ballot is cast, the voter is a registered member of that party unless they submit a signed request to the supervisors of the checklist to return to an undeclared status before leaving the polling place.

Individuals seeking the nomination of a political party at the State Primary Election should verify, before May 31, that they are registered as a voter in the town/city ward where they currently live and are registered as affiliated with their chosen political party.

Supervisors of the checklist are required to meet from 7:00 p.m. until at least 7:30 p.m. on May 31 to accept all party changes.

For more information on New Hampshire elections, visit www.sos.nh.gov/elections. New Hampshire’s 2022 State Primary Election will take place on September 13, 2022.