Where Legislators Speak Changes What They Say: Platform Conditions Climate Attention and Framing

Elected officials increasingly communicate across multiple social media platforms. We argue that platforms are not neutral channels: the same political pressures can be expressed differently across them. Using 6.19 million Facebook and X posts from 6,356 U.S. state legislators, we examine climate attention and stance. Ideology structures climate communication differently across platforms: in 2020–2021, liberal legislators devote substantially more climate attention on X, whereas ideological differences in climate stance are stronger on Facebook. These patterns persist among legislators observed on both platforms. Electoral and economic pressures also remain consequential. Electoral competition is associated with greater climate attention near Election Day without a detectable platform difference, while fossil-fuel exposure is associated with climate attention and opposition. These findings deepen our understanding of digital politics by showing that platforms are not exchangeable outlets for political messages, but part of the political context in which those messages take form.