02/12/2008 07:29 pm ET Updated May 25, 2011

Potomac Primary Results Watch

Live blogging will be light tonight (hopefully), to add whatever value we can to the much more current news you can get on television or major news sites.

First, here are the usual official exit poll links: MSNBC, CNN, CBS.

Second, Mark Lindeman has been running extrapolations for us each primary night using the publicly available exit poll cross-tabulations to get the overall estimate used to weight data. These overall numbers reflect the estimate the exit pollsters have the most confidence in at any moment. They are based on some combination of exit polls and pre-election polls as the polls close; they are based increasingly on a sample of actual vote returns as the night wears on. What we post here is probably stale. What we post here may be an hour or more behind what the network "decision desks" are looking at and use to call the race.

Updates will follow in reverse chronological order, all times Eastern.


9:34 - If you're watching television, you know that the networks have just called Maryland for Obama and McCain. Here, via Mark Lindeman, are the underlying vote estimates used to weight the cross-tabs just posted online: Obama 62%, Clinton 35% -- McCain 55%, Huckabee 29%, Paul 8%, Romney 7%.

9:21 - Reader Daniel T asks:

I just took another look at the CNN exit poll and now all the numbers havechanged but the number of respondents did not. The exit poll now showsMcCain winning 50% of the male/female vote when it showed Huckabee winningthe female voted before.

Can you explain why/how this happened?

Yes [though admittedly, this process is confusing]. Here is how I explained the process last week:

So I've alluded to the fact that these estimates improve over the course of the evening. What does that mean? It means that as the polls close, the estimates are based on some combination of results from the exit poll interviews and (believe it or not) pre-election poll averages. Once the polls close, the interviewers attempt to obtain actual results for their sampled precinct (or another "reporter" attempts to get the results from the county or state registrar). The exit poll analysts use these numbers to do two things: First, they gradually replace the exit poll results in their estimate models with the actual count precinct-by-precinct. They also calculate the "within precinct error" statistic for each state (or regions with each state - not sure) that are used to adjust exit poll results from the other precincts where actual count is not yet available.

The exit pollsters also have "reporters" who gather hard vote counts from a much larger random sample of precincts. All of this data goes into the computer models and is used to create various estimates of the vote. The "decision desk" analysts look at all of those estimates in deciding whether to "call" a race.

A separate operation within exit-poll-central takes whatever estimate they deem most trustworthy and uses it to weight the subgroup tabulations that we can read online. And we take those tabulations as they appear online extrapolate the estimates above from those tabulations. They typically do one updates 30 to 60 minutes after the polls close and another two or three over the course of the evening. All of this is a long-winded way of saying that what you are seeing here is not as current as the information the network analysts are using to make their calls.

8:51 - Call it "McShift:" After the calls for McCain by NBC, CNN and (presumably) the other networks, an update to the online cross-tabulations shows McCain head by eight points (49% to 41%). Keep in mind, as noted above, that updates to these tabulations run well behind the updates to estimates used to call he race, and the estimates improve as the exit pollster are able to incorporate actual vote returns into their random samples of precincts.

8:30 - Reader Andrew Therriault emails to point out something something minor but nonetheless noteworthy that reminds us that exit polls -- like all other surveys -- are subject to "measurement" error. Roughly 3% of the respondents to the Virginia Democratic exit poll provided answers that are not exactly consistent: They either support Obama but say they would be "disappointed" of Obama is the nominee, or support Clinton and say they would be "disappointed" if Clinton is the nominee. So, presumably, a small number of respondents did not hear these questions are intended (unless you have a better explanation).

7:44 - The initial estimate for the Democratic race in Virginia had Obama leading Clinton, 62% to 38% (Mark corrects me...either 61%-38% or 62%-37%).

7:43 - The tabulations that appeared for Virginia just after the polls closed showed McCain ahead of Huckabee by four points (46% to 42%) and Obama leading Clinton. An update that we noticed at about 7:30 showed Huckabee with a numeric advantage (46% to 44%), though we should stress that these differences are almost certainly not large enough to be statistically significant.