Persons otherwise qualified to vote at any primary election in any borough or township, except by registration or enrollment, shall be entitled to register and enroll as a member of a political party with the county commissioners at any time at least ten days before such primary election. The county commissioners shall, in such cases, register and enroll any such person as an elector of his or her proper election district in the same manner as electors are registered and enrolled by registry assessors.
25 P.S.§ 300