In order to vote in the Jefferson County Primary, you must be registered as a Republican.
https://idahovotes.gov/media/voter_registration.pdf

 

Unable to go to the polling place on Election Day? Request an absentee ballot.
Early in-person voting begins at the courthouse on April 30th. and ends on May 11th.
https://idahovotes.gov/media/2018_Primary_Absentee_Request_Form_Fillable.pdf