Here are three more sources that can help you understand the issue\
The Digital Marketing Institute is the educational facility that trains marketers and sales specialists in digital field. This Institute has a blog, in which it discusses various important global issues. The article that I advise to read explains how the social media is a shaping factor for politics, enhancing political campaigns for elections.
https://digitalmarketinginstitute.com/en-ca/blog/15-02-2018-how-social-media-can-enhance-political-campaign
Sysomos is Social Analytics division of Meltwater, a pioneer of media intelligence and Outside Insight. In the article of my choice it again explains how social media shapes politics, using examples to illustrate their points. It does not only explain how the social media influences politics, it also explains the why, and this is why I chose this article.
https://sysomos.com/2016/10/05/social-media-affects-politics/
This is an entire website designed to research the media effects on various spheres of life, including politics. This research was hosted in the University of Exeter, and this website includes the results of two researches that are constantly updated. The first is the Media Effects Research, which focuses on the effects of the media on everything, and the second is ‘Media in Context: and the 2015 General Election: How Traditional Media Shape Elections and Governing’, which addresses the strictly political side of the issue.
https://mediaeffectsresearch.wordpress.co
Here are my three choices, I hope you enjoy reading them.
Media and Politics 