In Texas, voters do not register by political party. Any partisan affiliation attributed to a voter is inferred solely from their participation in a party primary.
As of January 2026, Harris County had 2.7 million registered voters. Of these, 15.5% (419,643) have a history of voting in the Democratic Party Primary and 14.1% (382,583) in the Republican Party Primary. In total, only 802,226 of the registered voters have participated in a party primary. This means that approximately 70% of current registered voters have no primary voting history.
The tables below present the number of registered voters with a primary history, organized by Congressional Districts, State Senate Districts, State Representative Districts, Commissioners Court Precincts, and Justice of the Peace/Constable Precincts. Each table was produced by matching a compiled list of primary voters (2002–2024) to the January 2, 2026 voter registration roll.
The data may help contextualize voter turnout in Harris County primary elections and offer insight into how the level of partisan participation among voters may shape general‑election outcomes within individual jurisdictions across the county.
In the Lone Star state, political parties conduct open primaries. So, registered voters are not required to be members of a party in order to vote in a primary election. However, in any given primary election year, a voter may participate in only one party primary; voters cannot vote in both.
