Yes, Facebook can be used to influence elections and electoral results.
If i own a facebook page, i can literally ensure a post of my page reaches someone who was born in Gujarat , is now of 22-25 years old, lived in Bangalore currently living in Hyderabad Jubliee hills area ,part of some Congress fb group and also liked Modi, who is looking for some personal loan and looking to buy an apartment, likes Game of Thrones and also likes Night King , likes travelling but only visits Piligrim places, likes Mukesh Ambani but not Adani , shops for more of physical fitness items and attends Marathons.
Imagine that this data can be used by someone living in a far off place, creates a page, posts something and pays for ads in dollars or dirhams and influence a customer behaviour in India. When politics comes into it, this can get real ugly.
Everything you do on internet is tracked by 80+ ad companies via their cookies or track algorithms and your ad settings are defined by companies like Facebook and Google. Facebook App even analyses your voice conversations. There is also a famous pic of Mark Zuckerberg with his laptop mic and webcam sealed.
Looks at these if you want to be amazed about yourself 🙂
Facebook : Your interests tab of https://www.facebook.com/ads/preferences/
The recent issue with Cambridge Analytica was this data was shared/retrieved by them when facebook did not have good enough self regulations. This was used to create ad campaigns and influence people. Google is a bit better in this privacy self regulations.
If you want to look at what all data facebook and google have on you in detail, Guardian has a brilliant writing at https://www.theguardian.com/commentisfree/2018/mar/28/all-the-data-facebook-google-has-on-you-privacy
What we can only do is not get influenced by such social media posts and use our brain for a second before making a crucial decision or leaning towards a political ideology.