http://www.washingtonpost.com/blogs/the-fix/wp/2015/02/02/the-unsettled-republican-2016-field-in-four-unsettled-graphs/ By Philip Bump February 2
We are getting to the point in the 2016 election cycle -- three months old literally, older than time itself in figurative terms -- at which we can start watching polls to see what trends are emerging. Over the weekend, Pollster.com's Charles Franklin explored one way of comparing polls that we thought was worth exploring a bit deeper.
The link above goes to a version of this chart, which compares the October results of a Des Moines Register/Bloomberg poll of likely Iowa Republican caucus-goers with the results from a poll from the same pair released over the weekend.
The key part of the graph is the dotted line. Any (possible) candidate above that line improved since October; the percentage of the vote he received is higher than what he got in October. (They are all "he"s.) Below the line, and the percentage dropped. The further from the line, the bigger the effect.
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