Diffusion of innovation theory is used to explain adoption of Facebook in the 2012 campaigns for the U.S. Congress and to identify characteristics that differentiate the small subset of candidates who did not create a Facebook presence from the large majority who did. Models of Facebook adoption for House candidates reveal that there are no differences between Republicans and Democrats. Nonadopters are significantly more likely to be challengers or open-seat candidates, poorly financed candidates, candidates in noncompetitive races, and older. Among nonincumbents, Republicans, and candidates from Republican-oriented districts are more likely to adopt. This study serves as one of the first examinations of social media adoption by congressional candidates in the 2012 elections and discusses relevant developments and trends in adoption since Facebook’s introduction in 2006.