I've been progressively shifting away from recommending Facebook for candidates for a few months now. A new study suggests that it is almost worthless for brands. Here's an analysis of the study with a link to the actual study, which was done by Forrester Research.
Facebook is quickly shifting away from free publicity for brands (including candidates) and towards promoting paid ads. To get a lot of traction with Facebook, you're going to have to pay to promote your posts. And once you begin to pay to use Facebook, you need to weigh that against other forms of advertisement you're using.
Most candidates are advised to set up a Facebook account as soon as they decide to run so voters can find them. While it's certainly not going to hurt your campaign to have a Facebook page, you ought to be wary of how much time you devote to it.
I suggest having a link to your website on the Facebook page, and having any other relevant contact information. It doesn't take too much time to post 2-3 times a week about upcoming events or to post your ads when you create them.
But keep in mind that the people who like your page aren't undecided voters. They're politically engaged and probably partisan, and are liking your page because they intend to vote for you or already support your opponent and want to keep track of what you're posting.
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