Voters may or may not choose to affiliate with a political party. However, in order to vote in a primary election in the District of Columbia, you must be registered to vote with one of the parties that is eligible to conduct a primary election (Democratic, Republican, D.C. Statehood Green, or Libertarian).
18% of Washington DC voters are registered as “other” or with a 3rd party.
Details of voting in Municipal and Presidential primary elections:
Washington DC utilizes partisan primary elections. Over three-quarters of all municipalities have nonpartisan elections.
You must be registered with a designated party on or before the 21st day before the primary election, unless you are registering for the first time when you vote.