If you look at the polls, Comey's letter, which he had no requirement to send, tipped the election, from that point on the undecideds broke for Trump?   That's not a conclusion supported by inquiry. May 5th, 2017 Pollsters Find 'At Best Mixed Evidence' Comey Letter Swayed Election  The new report, from the American Association for Public Opinion Research, goes far beyond the Comey letter, however. More than a dozen pollsters and public opinion experts worked for months to determine what might have led polls to overestimate Clinton's support. They found that state-level polls were particularly far off from the final election results, leading many forecasters to overestimate Clinton's chances of winning. In response, the experts called for improvements in state-level polling to ensure that the polling profession doesn't suffer another "black eye" in coming years. ...state polls were off by an average of 5 points, the largest average since 2000. This is where the researchers drilled down into the whys of what went wrong. Late deciders in swing states ended up going significantly pro-Trump Part of the discrepancy between votes and polls was that voters did change their minds late — but it wasn't necessarily because of Comey. The decline in Clinton's support, the report finds, may have begun as early as Oct. 22, (three days after the final presidential debate) whereas Comey's announcement came on Oct. 28. That doesn't disprove that Comey's letter changed things, but it does suggest other factors were depressing Clinton's support at around the same time.  Another way error is introduced into polls is whether or not pollsters make the right adjustments for the current year.  One final factor that could have thrown polls off is turnout. Turnout patterns clearly boosted Trump. The counties where President Obama performed worst in 2012 had higher turnout increases, while the counties that highly favored him had lower turnout increases, as the report points out. The question is whether that different kind of turnout pattern threw off how pollsters adjusted their results. That seems plausible, said one researcher.  "To the extent that pollsters relied on 2012 as a model for the electorate either demographically or otherwise, there's the potential that that introduced error," said Mark Blumenthal, head of election polling for SurveyMonkey and one of the report's authors, at Thursday's event. "For that reason, our conclusion is that turnout probably was one of the two or three things that introduced error into this process; it's just very difficult for us to to quantify it. It's kind of an incomplete. It's a story that's not completely told."  Though many 2016 polls were indeed off, the authors hope it won't sour Americans on polling altogether. "The difficulties for election polls in 2016 are not an indictment on all of survey research or even all of polling," the report said.  http://archive.is/LcNJB http://archive.is/LcNJB#selection-4755.0-4764.2  I can't get to all your points/questions yet, but will try to put some responses put together when I can.