A distinct problem for American democracy is that voter participation rates remain higher among older, wealthier, and more highly educated citizens. Through their nonpartisan get-out-the-vote (GOTV) efforts, nonprofit organizations can help to remedy the participation gap, promoting higher turnout among under-represented voters. However, the literature reveals mixed evidence with regard to message content and its impact on turnout, and there is even less clarity about whether the method of message delivery matters for turnout. We find that nonprofit voter mobilization efforts are statistically linked to increased turnout, the odds of which increase when efforts center specifically on voter registration. While we find no overall effect of either message type (political efficacy vs. policy issue: immigration) or method of delivery (text vs. postcard) on voting behavior, the results show that there is a significant crossover interaction with political efficacy messages sent by text yielding the highest turnout.