We’ll stop having debates: how party organizations strategically invoke evidence

As the capacity to analyze data has mushroomed, invoking evidence to justify political opinions has gained popularity. How often do partisan organizations invoke evidence? How has this changed over time? I analyze the national party platforms from the two major American political parties since 1968 to assess when, how, and why the party organizations invoke evidence in their platforms. I introduce two categories for describing usage of evidence in partisan rhetoric: justification —citing evidence to corroborate the logic of existing ideological preferences—and solicitation —advertising interest in having more information to make a future policy decision. Using a novel dataset, I chart the frequency and style of how the two major parties invoke evidence in their platforms. I find stark partisan differences. While both parties primarily use solicitation—a finding that contradicts existing studies of individual political uses of knowledge—Republicans use justification at more than twice the rate of Democrats. I show this pattern accelerating after 1994. I argue that trends in how party organizations reference evidence reflect changes in values, goals, and policy commitments. Far from being neutral indicators of policy effectiveness, evidence is itself the product of and a tool for advancing a party’s agenda.