voter can change registration at the polls after voting, and can also change registration in periodic meetings of a town's Supervisors of the Checklist or at the City Clerk's office. These rules are designed to impede the casting of a cross-over vote for a different party, which may have the goal of sabotaging its nomination. Registering in a party constrains a voter's choice of ballot, but demonstrates support for the chosen party, and is a prerequisite to being a candidate of that party. Primary elections The famous New Hampshire primary is summarized in the article on New Hampshire. Nominations for all other partisan offices are decided in a separate primary election held in September of election years. In Presidential election cycles, this is the second primary election held in New Hampshire. Local government Municipalities New Hampshire comprises 13 cities and 221 towns, plus 25 unincorporated places. These governments conform to Dillon's Rule; that is, they are creatures of the state whose powers are limited to those expressly granted to them by law (NH RSA Title III). Municipalities also have powers necessarily implied by those express powers, and those essential to the local government's existence, but this authority is narrowly construed, in contrast to the practice in most of New England. For statistics on New Hampshire municipalities and comparisons to municipalities elsewhere in New England, see New England town. Cities are governed by Boards of Aldermen (in Manchester and Nashua) or City Councils (all other cities). In towns, the executive power is the Board of Selectmen, except that some towns, especially larger ones, are governed by a Town Council. The Town Meeting is effectively the municipal legislature, of which every registered voter is a member. Town Meeting approves, amends, or rejects the items on the warrant, which must be published in advance. Articles can be placed on the warrant by the town's executive board or by citizen petition. Town Meeting meets annually, normally on the second Tuesday in March, to set the year's budget. Special Town Meetings can be called to deal with urgent transactions. The municipal election, which selects town officers for the coming year and may approve changes to local law such as the zoning ordinance, is thought of as a session of the Town Meeting. Government by referendum (SB 2) Since 1995, a town may elect to govern itself by Official Ballot Referenda. This procedure is known as