Ok. At 2am EST, this showed up on top of my #facebook feed. This
  is the first time I've seen this. Facebook conducts social
  experiments and has control over feeds. Now, yes, I am
  registered. Independent. No primaries for me so all of the news
  about the gaggle of candidates amounts to gossip for me
  generally. I wait until it's decided to two via the primary
  process and even then, not until I close the curtain behind me.
  I may have some idea but I don't want to influence anybody else
  nor do I want anyone to try to influence me. Considering the FB
  customizes my feed, I do not want to give them a data point that
  gives them a clear indication of my stance. Let their AI figure
  it out. But I do my voting at the polls, not for Facebook's
  large public experiments. I wouldn't care if it wasn't for their
  Internet org and "free basics" efforts in India. I'm not happy
  with those practices and I'm glad India took a stand and said
  they'd rather work on a full Internet for their people rather
  than a restricted subset. So, there's my politics. I don't think
  it's bad if someone answers their questions but for me
  personally? I don't want to make it any easier to be part of
  their social experiments. I like FB and use the service but I
  believe in a transparent Internet. Perhaps I'm a holdover from
  1990-93 dreams of open culture on the Internet but I still
  believe in it. ======
  Also, the choice of button colors. Facebook generally has a
  Democratic leaning. Blue is code for Democrat, Red is code for
  Republican. The surrounding of the blue with the red circle is
  not accidental. Ring of republicans surrounding Clinton and
  Sanders.I suppose as an Independent, I am the white ring. Even
  beyond the 6 second analysis, this is a subtle social pressure.
  Conveys a sense of urgency. Sharing is emphasized - it's on the
  right-hand side. Mind you, I'm not disagreeable to these ideas
  generally but subtle social engineering can be very annoying. ==
  I'm not creeped out by it - I just know that FB doesn't waste
  good opportunities for research for future papers. So far,
  online hasn't made much impact in elections. But this time, it
  is. They're not going to waste an opportunity to put at least a
  FEW extra dollars in overtime for a graphic designer to meet
  with a social psychologist to maximize implicit association. ==
  The point is: It's supposed to be very subtle. It's a little pat
  of encouragement. If you're already democrat or have leanings
  that way, you probably won't even spot it. Even a republican
  will likely miss it. But, I'm neither party. It jumps out. The
  choice of light blue/dark blue. Once the candidates for each
  party are set, you won't see that button again - I'd almost bet
  $, except I don't like betting tongue emoticon ==
  *
  [1]votez

References

  Visible links
  1. http://icopiedyou.com/wp-content/uploads/2016/02/votez.jpg