Using CNN, your last example, if you look at the lower data on this site, you’ll see that they have CNN bias recorded at 7.1%.
That would be claiming that CNN had decreased their Hillary bias and then increased it again.
It would seem to be, in my opinion, looking at the chart, an attempt to show a Trump convention bounce and then to take it away again.
I am on my mobile right now. Need to get to the PC with excel. I think these folks have tapped into something interesting, in that consistent bias is better in that the pollsters are true believers. Inconsistent bias is indicative of DNC generated agendas. Any secondary analysis should take that into account