The Idaho Secretary of State issued a clear judgment about changing party affiliation for the March 10, 2020 Presidential Primary. The ruling states that if you are registered with a specific party, and you wish to change your party affiliation in order to vote on a different ballot, there is no deadline. If you are unaffiliated, you may choose the ballot of any party. However, your choice of ballot becomes part of the public voting record. Also, there is no Independent Party in Idaho. Therefore, to be considered an Independent voter in Idaho, you must be registered as unaffiliated with any party.
The last day to change your party affiliation in time for the May 19, 2020, primary for state and local offices is March 13, 2020.
A choice of ballot according to political party affiliation happens only in primary elections. In general elections voters do not choose among parties; candidates chosen by their respective parties in the primary are listed on the general election ballot. (The general election is held in early November.)
A Party Affiliation Change Form on the Kootenai Elections website.