I don't know if it is a bot, but I have seen other people post several screen captures of Twitter tweets that were exactly the same. Not a reTweet, but a Tweet with the same text. It could have been political marching orders.
Quick! Go to Twitter and post this to support our cause!!
Or, it could be bots.
Of course, there was that big scandal of Facebook adjusting timelines to show things that slanted towards Facebook's views. Twitter does it with the Trending items. So, technically, I guess those are bots as well.