Yup. Primaries are the key.

Democratic primaries see less than 15% turnout in congressional elections, yet people wonder why nothing changes. Do you know who always shows up? Retirees, and they have very different needs than the working class.

30/50 states have closed primaries, meaning you must be registered as a Democrat to vote in the Democratic primary. Check your state’s primary type here: https://ballotpedia.org/Primary_election_types_by_state