HB 951 introduces a requirement for voters in Texas to declare a political party affiliation in order to vote in that party’s primary election or participate in its internal affairs. The legislation amends voter registration procedures to include an affiliation declaration and requires this information on registration certificates and voter rolls. Affiliation with a party will be necessary to serve as a delegate, participate in party conventions, or be a candidate in that party's primary election. The bill also specifies penalties, including criminal offenses, for voters attempting to participate in a party's primary election without the required affiliation. Additionally, the bill outlines procedures for maintaining and changing party affiliation, which will be reflected in voter registration records starting in 2026. It also directs counties to notify voters of these new requirements and provides mechanisms for unaffiliated voters to update their status. The effective date of this legislation is September 1, 2025​.