Analyzing Public Opinion and Emotions Using Tweets and Online-Comments toward Candidates in 2017 South Korean Presidential Election

The 2017 Korean presidential election was different from previous presidential elections for two reasons: First, it was a by-election due to the unprecedented impeachment of the president Park Geun-hye, and second, more than three candidates from multiple parties competed in the election. Since Moon Jae-in was predicted to easily win, the fight for the second place - between Hong Joon-pyo and Ahn Cheol-soo - was very competitive. In order to understand the electoral dynamics, we collect and analyze tweets and online-comments toward major candidates with logic of granger causality. We find that public sentiment toward Ahn does Granger-cause changes in online sentiment toward other candidates both from major and minor parties. This result shows that Ahn played a pivotal role in the 2017 presidential election, and implies that Koreans are eager to have alternative forces.