Social media is changing the business of representation in the Senate. If you want to know what your senator is up to, you don't need a newspaper, just your phone. Some senators are social media minimalists while others are digitally long-winded, but each senator has the ability to insert themselves into our daily digital routines and frame their political brand for a public audience. Drawing on a unique dataset of almost 200,000 senator tweets, Tweeting is Leading offers a critical analysis of senators' communication on Twitter, the individual and constituent forces that shape it, and the agendas that result. The public priorities that senators communicate through social media - what Annelise Russell calls their rhetorical agenda - offer a necessary tool for understanding how senators link their carefully crafted public image with potential voters. The rhetorical agenda challenges what we know about representation, removing the institutional and political constraints on congressional communication and giving lawmakers a messaging platform where individual discretion is high, the relative costs are low, and someone is always watching. Tweeting is Leading emphasizes why representation on social media matters for understanding media norms and how lawmakers digitally build a political brand, showing empirically how senators self-constrain their communications to curate different styles of representation that match constituent expectations.