We are past the time when polls were a snapshot of the “horse race” or a barometer on public opinion. They are now a campaign tactic and you have to follow the money.
1) Dems do outnumber R’s in registration nationally. A D+x (some number) is not oversampling. The value of x is debatable but it is not zero. 2012’s turnout was D+about 6. A pollster who uses it may be wrong because she won’t perform as well as Obama, but it’s a reasonable thing to use.
2) 3% shift in one day means the sample picked up a lot of Clinton voters or lost a lot of Trump voters on one particular night. Maybe it appeared or Trump’s good night rolled off.
3) If it’s the former . . . a good night for Clinton, it will roll off by Tuesday, when a rather better poll is taken.
4) The Friday announcement of last week, recall, DIDN’T SAY ALL THAT MUCH. More evidence found to examine. Not “WE’RE INDICTING”. It would not move many votes, and remember a LOT of votes have already been cast. That announcement absolutely wasn’t enough to have people in the few states that allow a revote to bother changing.