The adoption of social media in political marketing has grown dramatically over the past ten years, as it creates two-way communication that stimulates and fosters candidates’ relationships with voters. However, can the count of “supporters” and “likes” recorded on the Facebook page of a candidate predict whether he/she will win the elections or not? In view of this, predicting an electoral outcome using “big” social media data is a new research topic that has emerged due to the exponential growth of social media. This study examines the extent to which political candidates’ use of Facebook fan pages and interaction with their supporters are related to the election outcomes (vote share and election success) of Taiwan’s 2016 legislator election campaign. Facebook data were acquired for all 354 candidates. The findings indicate: a candidate’s Facebook presence is related to his/her election outcomes. Positive correlations were also observed to exist between the numbers of supporters/likes candidates secured on their official fan pages and their popular vote share. Moreover, the “net-fans ratio” preliminary model, based on a candidate’s likes/supporters and excluding those repeated with respective opponents, has an explanatory power to forecast regional legislators’ election outcome with 81.5% accuracy of all the seats, and with 87.9% accuracy of the seats of 6 major municipalities. Hence, Facebook data could be a significant indicator of electoral success.