Research Brief: Primary Voters Elect Most of Congress. They're Not Like Most Americans.

Key Takeaways

• In 2024, 87% of Congressional races were decided in primary elections – meaning the 7% of voters who participated in these elections effectively chose the vast majority of the U.S. House. New analysis of Catalist voter file data illustrates just how unrepresentative these voters are compared to the general voting age population.
• While a plurality of Americans identified as independent or nonaffiliated, they were significantly underrepresented among these decisive primary voters; independents made up 39% of the voting age population but just 11% of the electorate in decisive primaries.
• While 47% of the voting age population identified as moderate, just 11% of decisive primary voters did so. By contrast, self-identified liberals made up 20% of the population but 29% of decisive primary voters, and conservatives comprised 33% of the population but 60% of the decisive primary electorate.
• Decisive primary voters were also demographically unrepresentative, being significantly older, whiter, wealthier, and more educated than the population at large.

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Figure 1: Only 7% of Voting Age Americans Were Decisive Primary Voters

Figure 2: Independents Were Significantly Underrepresented in Decisive Primaries

Figure 3: Decisive Primary Electorates Were Four Times Less Moderate than the Population

Figure 4: Decisive Primary Electorates Were Much Older than the Population

Figure 5: Nonwhite Voters Were Underrepresented in Decisive Primaries

Figure 6: Decisive Primary Voters Were More LIkely to Have Higher Incomes

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