WASHINGTON -- The final round of polls on Tuesday's Wisconsin recall election are something of a puzzle, although the uncertainty is more about the margin separating the candidates than the outcome. While virtually all show Republican Gov. Scott Walker leading his Democratic challenger, Milwaukee Mayor Tom Barrett, they disagree about the size of Walker's lead.
Six polls completed in the last 10 days have shown everything from a 12-percentage-point Walker lead to a dead-even race. One explanation for the difference is sponsorship: Internal polls sponsored by the Democratic campaigns have typically shown a closer contest. Beyond that, although the polls differ considerably in their methods, nothing stands out to explain why some show Walker doing better than others.
With all polls included, the HuffPost Pollster chart of publicly released Wisconsin surveys gives Walker a lead of 3.8 points (50.4 to 46.6 percent). With the polls funded by the Democratic campaigns excluded, Walker's lead grows to 6.4 points (51.7 to 45.3 percent).
In particular, several internal polls conducted by the Barrett campaign or funded by its allies have shown a considerably closer race than those sponsored by media outlets or otherwise not funded by one of the campaigns.
The difference has been evident throughout the campaign. Surveys sponsored by the Democrats and their allies have typically shown a margin about five percentage points narrower than those conducted by more independent outlets.
That difference is also consistent with the pattern of statistical bias in publicly released partisan polls, which typically skew the results a bit, boosting their sponsor by about three points and dropping their opponent by roughly the same amount.
Keep in mind that the distinction between partisan and independent can be relative. Our charts treat the Wisconsin polls by Public Policy Polling and We Ask America as independent because they lack partisan sponsors. Elsewhere, however, PPP has polled for local Democratic campaigns, and We Ask America is a subsidiary of the Illinois Manufacturers Association. The former has Walker leading by three points on its final poll, while the latter has Walker up by 12.
Can we gain any insight into the differences among the polls' results by considering their methods, particularly the way they select "likely voters"?
The Marquette University Law School polls used a very simple procedure. They selected those respondents who said they were "absolutely certain" to vote in the recall election as likely voters. The rest -- including those who described their chances of voting as "very likely" and just "50-50" and those who said they would not vote -- were considered unlikely to vote.
The Marquette pollsters also weighted their full adult sample to conform to U.S. Census estimates of the demographics of the state's adult population, including sex, age, marital status, race, Hispanic origin and education. They used live interviewers and called samples of landline and mobile phones using randomly generated numbers, which gave all working phones in Wisconsin a chance of inclusion.
The We Ask America polls used an even simpler method to select likely voters. According to We Ask America's Gregg Durham, the survey's recorded voice queried each person answering the phone if he or she was "a registered voter who plans on voting in the recall election." Those who pressed the appropriate button to say no were dropped from the survey.
We Ask America also sampled differently. It drew from Wisconsin's list of registered voters and then weighted the results from the completed interviews by gender, age, race and Hispanic ancestry. Durham said We Ask America used "the latest census data" to inform its weighting targets, but since voters differ demographically from the full population, the pollsters "kind of blend it based on the best available info."
The automated PPP surveys used a similar method. Those who answered the phone in sampled households heard a recorded voice say, "This is a short survey about Tuesday's recall election for governor. If you don't plan to vote in the recall election, please hang up now." Those who remained on the line were considered likely to vote.
PPP also sampled from the official lists of registered voters, but the firm added an extra step. It limited its selection to households with at least one voter who had actually voted in at least one of the last three general elections: 2006, 2008 or 2010. PPP also adjusted the demographics of the final sample -- age, race and gender -- using a combination of calling quotas and weighting. The weighting targets are based on "who responds to the poll, past election patterns, census," according to PPP's Tom Jensen. "It's just a combination of factors."
The Angus Reid survey made no special effort to identify likely voters: It reported results for all self-identified registered voters. The survey was very different, however, in that it was conducted over the Internet with Wisconsin voters who had previously volunteered to complete surveys as part of Angus Reid's "Springboard America" panel. Thus, only voters with Internet access who had previously joined the Angus Reid panel had a chance of being selected.
The polls sponsored by the Barrett campaign or allied campaign committees were conducted by Garin-Hart-Yang, Lake Research Partners and the Mellman Group. The polls' press releases disclosed very little methodological information and almost nothing about how likely voters were selected. The Lake Research release said it conducted an "automated survey" over the Memorial Day weekend. The Mellman release indicated that the firm sampled from a registered voter list. Neither Garin-Hart-Yang nor Lake Research responded to our requests for further information.
All of these methods involve trade-offs. The advantage of the Marquette Law School methodology is that it allows virtually all potential voters some chance of inclusion and requires no assumptions about turnout or voter demographics. Likely voters simply identify themselves. The downside is that not all of those who cast a ballot will describe themselves as "certain" to vote, and many deemed not likely to vote will cast a ballot.
In theory, pollsters who sample from registration lists improve the accuracy of their likely voter selection because they have cut out the nonregistered. They can also go the added step of limiting their sample to those with some past voting history.
Some polling experts argue that the anonymous nature of automated surveys produces a more honest answer to questions about voting intent. But the method has its own flaws, including the cost of missing the voters whose phone numbers are unlisted or cannot be matched to official records, including most of those who have cellphones but no landline service.
The bottom line here is that all of the independent Wisconsin polls used relatively simple methods of identifying the probable electorate. None followed the more complex but controversial Gallup likely voter model. If the partisan pollsters believe some aspect of their methodology is behind their closer numbers, they have not offered that explanation.
Again, the polls without partisan sponsorship put Walker ahead by an average of six points. Given that margin, as Nate Silver of The New York Times noted, "the historical accuracy of gubernatorial polls over the past 15 years" puts the odds of a Walker victory at "almost 95 percent."
Below, more on the history of the Walker recall effort:
In 2010, a surge of Tea Party momentum and backlash against Democrats helped elect conservatives including Wisconsin Gov. Scott Walker, who became the state's first Republican governor since 2002. Walker promised to cut taxes and create 250,000 new jobs, but a deeper look into his past also showed a politician who had inflamed tensions with unions before. The Washington Post reports on his time as Milwaukee County Executive, during which the collective bargaining rights of unions already appeared to be one of his most ambitious targets: During his eight-year tenure in Milwaukee County, Walker never raised property taxes. He cut the county workforce by 20 percent, improved its bond rating and gave back hundreds of thousands of dollars of his own salary as part of the effort to trim spending. But he also saw his relations with local unions deteriorate. Union leaders say Walker never negotiated in good faith and had a singular solution to every budget problem: cut. Under his watch, the county privatized public jobs, laid off workers and placed others on furlough. [...] Walker argued that collective bargaining was the biggest hurdle to balancing the budget and that unions had little incentive to give ground because they almost always prevailed in arbitration. He said that the cuts he proposed were intended to prevent layoffs and accused union leaders of being uninterested in compromise.
After taking office, Walker announced a number of controversial proposals, including eliminating collective bargaining rights for state employees and reducing public employee benefits, as part of a "budget repair bill." He said the reforms were necessary to prevent the layoffs of thousands of workers. Facing anger from unions, Walker announced his readiness to mobilize the state's National Guard in response to any disruptions. The announcement was met with backlash by public sector workers across the state.
The fight over Walker's proposed budget was contentious, with Wisconsin Democratic state senators crossing state lines to Rockford, Ill. in an attempt to stall the vote. In March 2011, Walker signed the budget, significantly curtailing collective bargaining rights for union-affiliated public employees. Thousands of protesters gathered in Madison, and labor leaders and Democrats vowed to fight back.
In the months following his signing of the bill, Walker's opponents organized, announcing their intentions to recall the governor and his supporters. They erected a tent city and believed they'd won a surprise victory over a conservative state supreme court judge, before amended voting totals from one county reversed the victory. Walker continued to defend his policy but said he had made mistakes in the political execution. Correction: A previous version of this text inaccurately stated the final results of the Supreme Court race.
Wisconsin Democrats scored a victory in their attempt to unseat Republican state legislators when they defeated six "fake" Democrats running in the party's primaries. Four of the six Republicans targeted for recall held onto their seats in the general election.
Petitions to recall Walker and his lieutenant governor gathered nearly a million signatures each, far exceeding the 500,000 needed. Election officials ordered a recall election.
Democratic candidates are now fighting for the chance to face Walker in the recall election. Amanda Terkel reports: Recalling a sitting governor is no easy task; it's been done just twice in U.S. history. But while Republicans are amassing money and ground support in the next few months to fend off the opposition, Democrats are still figuring out who among them will be the strongest candidate to run against the governor. The process is pitting traditional allies against each other, as the candidates try to show off their pro-labor credentials while also making the case that they are best equipped to beat Walker in the general election. There are currently four Democratic candidates competing in the May primary. Former Dane County executive Kathleen Falk and Milwaukee Mayor Tom Barrett are considered the two frontrunners, with state Sen. Kathleen Vinehout (D-Alma) and Secretary of State Doug La Follette also in the race.
After a tough primary, Milwaukee Mayor Tom Barrett bested three other Democratic candidates in an early May primary. HuffPost's Amanda Terkel reports: Barrett beat former Dane County executive Kathleen Falk, Wisconsin Secretary of State Doug La Follette and state Sen. Kathleen Vinehout (D-Alma) in the Democratic primary. The Associated Press called the race for Barrett shortly before 10 p.m. Eastern time. Barrett's victory set up a rematch with Gov. Walker, who he lost to by about 5 percentage points in 2010.
HuffPost's Mark Blumenthal reports: Wisconsin Gov. Scott Walker (R) holds a narrow lead over his Democratic challenger, Milwaukee Mayor Tom Barrett, in the run up to Tuesday's recall election, according to the final poll on the race conducted by Public Policy Polling, a firm affiliated with the Democratic Party. PPP's automated, recorded-voice survey, conducted among 1,226 likely voters over the weekend, puts Walker at 50 percent support, 3 percentage points ahead of Barrett's 47 percent. Fifteen surveys on the recall election have been released over the past month, and while most have produced close results, all but one have given Walker the advantage. Independent polls have generally given Walker a bigger lead than the handful of publicly released internal polls sponsored by the Barrett campaign or its Democratic allies.
After a whirlwind day of voting that featured swarmed polling places around the state, media outlets called the race for Walker less than an hour after polls closed in the Badger State. Walker's lieutenant governor, Rebecca Kleefisch, was also declared victorious in her recall contest.