Section 70B. In any year in which candidates for presidential electors are to be elected, the selection of delegates and alternate delegates to national conventions of political parties shall be by that system adopted by the state committee, provided such system shall not include the placing of the names of delegates on the presidential primary ballot; and provided, further, that the distribution of delegates under any such system shall reflect the preference expressed by the voters on the presidential preference portion of the ballot at the presidential primary. The system adopted by the state committee shall be set forth in written rules and procedures covering all aspects of the delegate selection process and a copy of such rules and procedures shall be filed with the state secretary on or before October first of the year preceding the year in which presidential electors are to be elected. The number of district delegates and alternate district delegates, not less than two from each congressional district, and the number of delegates and alternate delegates at large shall be fixed by the state committee, who shall give notice thereof to the state secretary on or before the first Tuesday in January. At such primaries, members of the state, ward and town committees shall also be chosen as provided in chapter fifty-two.