The first Democratic Presidential Debate of 2016 occurred 10 days ago on October 23rd; since then, 5 new polls have been conducted in New Hampshire and 2 in Iowa. Before I cover the new polling, several individuals made some important announcements pertaining to the Democratic nomination process; these also led to some site improvements and a methodology clarification.
On October 20th, Jim Webb announced that he was suspending his campaign:
And I know I’m going to hear it, so let me be the first to say this: I fully accept that my views on many issues are not compatible with the power structure and the nominating base of the Democratic Party. That party is filled with millions of dedicated, hard-working Americans. But its hierarchy is not comfortable with many of the policies that I have laid forth, and frankly I am not that comfortable with many of theirs.
For this reason I am withdrawing from any consideration of being the Democratic Party’s nominee for the Presidency. This does not reduce in any way my concerns about the challenges facing our country, my belief that I can provide the best leadership in order to meet these challenges, or my intentions to remain fully engaged in the debates that are facing us. How I remain as a voice will depend on what kind of support I am shown in the coming days and weeks as I meet with people from all sides of America’s political landscape. And I intend to do that.
So here we are. I’m stepping aside from the Democratic primary process, but I will never abandon my loyalties to the people who do the hard everyday work of keeping our country great. And we will see what happens next.
Source: Jim Webb 2016 
Webb's withdrawal is not surprising given his low polling numbers and his generally poorly received debate performance.
The next day, October 21st, saw a bigger announcement pertaining to Joe Biden's nomination campaign, or rather the lack thereof:
In a hurriedly arranged speech in the White House Rose Garden with President Obama at his side, Mr. Biden said that he and his family had overcome their grief at the death of his elder son enough to commit themselves to the rigors of a campaign. But with just days until the first filing deadlines, he said he had concluded that it was simply too late.
“Unfortunately, I believe we’re out of time, the time necessary to mount a winning campaign for the nomination,” Mr. Biden said. “But while I will not be a candidate, I will not be silent.”
Indeed, he used the rest of his 13-minute speech to outline the case he would have made as a candidate and even take a few implicit jabs at Mrs. Clinton over her hawkish foreign policy, hostility to Republicans and breaks with Mr. Obama on certain issues.
Source: NY Times 
While Biden never formally announced his intent to seek the nomination, his name was included as a potential candidate in pretty much every poll conducted pertaining to the Democratic nomination. Biden's implicit candidacy created some ambiguity as to the most pertinent or valid polling results; the basic question was, should Biden's presence be included? Some pollsters included Biden, some didn't, and some asked two sets of horse-race questions.
I answered this question by tabulating the results from the first nomination preference question within the survey; I did this for two reasons. (a) The order chosen by the pollsters reflects their implicit determination as to which candidate list they deemed to be most pertinent; and (b) The site does not have the capability, currently, to dynamically apply different polling outcomes across multiple candidate lists. This capability is certainly possible, but at this point in time, the usefulness does not overcome the time required to implement.
On a site improvement note, I've adjusted the matchup pages to excluded withdrawn candidates by default.
The final withdrawal announcement came from Lincoln Chafee, on October 23rd:
"As you know, I have been campaigning on a platform of Prosperity Through Peace," Chafee said at the DNC's annual Women's Leadership Forum in Washington. "But after much thought I have decided to end my campaign for president today. I would like to take this opportunity one last time to advocate for a chance be given to peace."
Source: CNN 
This leaves 4 officially declared candidates in the race and two front runners; Hillary Clinton and Bernie Sanders. I posted a table last week with the current regressions for each candidate in Iowa, New Hampshire and South Carolina. I've taken last week's table and compared it with the new regressions with the inclusion of polling conducted after the first Democratic debate; there was no new polling from South Carolina. I have removed withdrawn candidates, Webb and Chafee, as their data was not interesting, but left Biden out of curiosity:
|Iowa President||Hillary Clinton (D)||Martin O'Malley (D)||Joe Biden (D)||Bernie Sanders (D)|
|New Hampshire President||Hillary Clinton (D)||Martin O'Malley (D)||Joe Biden (D)||Bernie Sanders (D)|
Bernie's numbers plummeted in New Hampshire, although he still leads by 5.81%, but his numbers increased in Iowa where he now trails by 2.59%.
Without concentrating on individual candidates, it's interesting to note that male reactions were almost twice as strong. The standard deviation of the percentage change by gender, in the candidates listed in the tables above, is 4.82% for males and 2.7% for females.
This concept of volatility can also be seen at the candidate level as well. Bernie's confidence bands have a much wider range of uncertainty than those of Clinton:
I don't have an empirical explanation for why Bernie's uncertainty is greater. My simple and naive reasoning is that support for his candidacy is drawn from a strong Pro-Sanders crowd but also augmented by an Anti-Clinton bloc. Clinton on the other hand is the establishment candidate so her support is less multidimensional; you either support her or you don't. To put it more concisely, the complexity of each candidate's support is reflected in their uncertainty, and I think it's fair to say that Bernie's support is much more complex than Hillary's.
Updated on October 24, 2015 at 8:09:58 PM CT