I wonder why you quoted Brietbart - which is highly partisan and often skewed - vs ABC so we can review the ABC comments and methodology.
But no harm, as Breibart had a link to the ABC poll.
Yeah - this is a monster move, especially when considering the movement occurred within the same poll, and only 4 days apart!
Other polls are also showing big intra-poll movement, including Fox, so something's definitely shaking here. And as you mentioned, these recent polls are pre-Comey announcement.
After reading the poll itself, it appears quite a few things are happening, but predominate is 'likely turnout' spiking for Trump, and conversely dipping for HRC. The Trump spike seems to reflect alienated Republicans coming back home, including women.
It's powerful stuff.
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Here's the ABC poll, itself:
ABC WaPo: 2016 Election Tracking No. 7
And here's the link to it's release and commentary on ABC:
ABC News: Shift in the Electorate's Makeup Tightens the Presidential Contest (POLL)