President Obama maintains a slight lead over Mitt Romney according to the most recent national polls. An average of five polls released over the last two weeks has President Obama with 46% of the vote compared to 45% for Mitt Romney. A Real Clear Politics average of six polls from the last month has Obama ahead 46.4% to 45.1% for Romney. President Obama’s lead has remained relatively unchanged from last week’s update, when he also had a lead of just over one point.
However, all polls are not created equally. The methods of each pollster vary, and many pollsters will adjust their numbers after their survey is complete. Ideally, these adjustments make the poll more accurate, but that is not always the case Finally, many pollsters also have a track record for either accurately predicting elections, or favoring one side over the other
As new polls are released, I will be providing continual updates, posting each poll along with some analysis on each pollster’s past reputation and performance. To receive more updates, follow me on Twitter or Facebook. I will also provide analysis on the latest trends.
Poll of 1500 “likely voters” taken from 7/27/2012 to 7/29/2012
- Romney 47%
- Obama 45%
Analysis: Last week Rasmussen had Romney with a one point lead. Over the last seven days Rasmussen had Romney’s lead growing to four points, but their most recent update has Romney’s lead back down to two.
Rasmussen uses a fairly large sample and by “tracking” their results over multiple days the pollster should be able to produce more accurate results.
However, Rasmussen’s poll uses a “likely voter” sampling method, which excludes some registered voters. In the past, Rasmussen has been accused of producing biased results that tend to favor Republican candidates. Rasmussen does not include cell phone users, but attempts to compensate by using an “online survey tool to interview randomly selected participants from a demographically diverse panel.”
In 2008 Rasmussen’s final poll matched up well with the final result in the race, and its polls in the final month were fairly consistent. However, in 2010 a study done by the American Research Group found Rasmussen to be the least accurate of the eleven pollsters they evaluated. Rasmussen uses a sample that has “baseline targets” of 35.8% Republicans, 33.0% Democrats, and 31.2% “unaffiliated” voters, despite other surveys that show Democrats’ actually outnumbering Republicans in the general population.
Poll of 3050 registered voters taken from 7/20/2012 to 7/27/2012
- Obama 46%
- Romney 46%
Analysis: Last week Gallup had President Obama with a two point lead, which has now shifted to a tie according to their data.
Gallup has, by far, the largest sample size, with 3050 registered voters, which theoretically should make their poll more accurate. Gallup includes date from six days, which theoretically will even out their results, but the large date range could also be including old/bad data.
Gallup’s polls varied greatly in the 2008 race, at one point having McCain ahead by ten points before producing a final prediction with Obama up by eight points. Gallup has not released the internal breakdown of their sampling. Gallup was rated above average by Nate Silver in 2010.
NBC News/Wall Street Journal
Poll of 1000 registered voters taken from 7/18/2012 to 7/22/2012
- Obama 49%
- Romney 43%
Analysis: NBC News/Wall Street Journal’s poll has by far the largest for President Obama among the most recent polls. This pollster has consistently shown Obama with a lead of at least three points, even when other pollsters have had the race closer.
The poll includes all registered voters which may favor the Democratic candidate. In 2008 NBC New/Wall Street Journal scored fairly well in terms of accuracy and consistency in predicting the actual results in the final month of the election. Nate Silver of The New York Times gave these pollsters an above average rating in 2010.
Poll of 901 registered voters taken from 7/15/2012 to 7/17/2012
- Obama 45%
- Romney 41%
Analysis: Fox News has a reputation for favoring Republican candidates, but over the last few months their polls have actually shown some of the largest leads for President Obama. In this case, Fox News shows a larger lead for Obama than any of the other most recent pollsters, including NPR and CBS/N.Y. Times.
At the same time, the Fox News poll has a very large number of undecided (14% of their sample), which likely includes many Romney voters who simply have not committed at this point.
In 2008 Fox News performed well in terms of accuracy, but not well in terms of consistency in predicting the 2008 presidential election. In his June 2010 ratings, Nate Silver rated Fox News as right at the average mark for a “Default/New Pollster.”
CBS News/N.Y. Times
Poll of 942 registered voters taken from 7/11/2012 to 7/16/2012
- Romney 47%
- Obama 46%
Analysis: The CBS News/NY Times poll was taken of 942 registered voters and included cell phone users. The sampling should therefore favor President Obama, but their poll actually shows Romney with a one point lead.
CBS/NY Times did not release a breakdown of how their sample was split up between Republican and Democratic voters. In 2008 CBS/NY Times was one of the least accurate and consistent pollsters in the final month of the race. CBS/NY Times was rated above average by Nate Silver in 2010, but below Rasmussen, Gallup, and NBC/Wall Street Journal.