The 17th Amendment established the direct election of senators. Although scholars have discounted the Amendment as inconsequential, we argue that it significantly changed patterns of election-seeking and legislative voting behavior. First, the Amendment negated the influence of state legislatures in senators' decisions to stand for reelection, inducing more incumbents to run. Second, the Amendment introduced incentives for senators to moderate their public ideologies in pursuit of reelection. We employ a selection model to test the impact of the 17th Amendment on the interdependent decisions to stand for reelection and to shift late-term roll-call behavior. Using W-Nominate scores for major party senators serving from 1877 to 1932, we show that post-Amendment senators, particularly Republicans, were systematically more likely to moderate ideologically as elections approached.