For each primary, the Supervisor of Elections shall furnish to the board of elections of each legislative district sample ballots of each party in similar form to the official ballot, printed on white paper and without the facsimile endorsement of the Supervisor of Elections, equal in number to one-fifth of the number of ballots cast for each political party in the preceding primary election for each polling district within the legislative district. The sample ballots shall be of the same size and form as the official primary ballots.