Accurate polling can be difficult, but some pollsters fare better than others each election year.
One Michigan polling firm had an especially rough year, though.
The New York Times’ Nate Silver found that Foster McCollum White Baydoun, a Troy-based polling firm that conducted surveys on behalf of WJBK-TV, had an 8.6-point bias toward Republican presidential nominee Mitt Romney in the last 21 days of the campaign.
Though the firm is listed as a Democratic pollster by Real Clear Politics, Foster-Baydoun found Romney with a one-point edge in its final Michigan poll. President Barack Obama won the state by 9.5 points last Tuesday, and Obama campaign officials dismissed the group’s polls all year.
Another Michigan pollster, the Glengariff Group, which polled for the Detroit News, rated among the worst in the nation with a 5.8-point Republican bias.
Overall, Silver found polls over the last three weeks of the campaign had a roughly two-point bias toward the GOP. He said there could be several reasons why, including Hurricane Sandy devastating a reliably Democratic region and making polling more difficult on the East Coast, but firms that fail to contact voters via cell phone might be the main cause.
“Research by polling firms and academic groups suggests that polls that fail to call cellphones may underestimate the performance of Democratic candidates,” Silver wrote last week. “The roughly one-third of Americans who rely exclusively on cellphones tend to be younger, more urban, worse off financially and more likely to be black or Hispanic than the broader group of voters — all characteristics that correlate with Democratic voting.”
Among more well-known polling firms, Gallup performed the worst of any by far, according to Silver’s analysis. Gallup’s 11 likely voter polls in the final month of the campaign averaged a 7.2-point bias toward Romney.
“Gallup has now had three poor elections in a row,” Silver wrote. ”In 2008, their polls overestimated Mr. Obama’s performance, while in 2010, they overestimated how well Republicans would do in the race for the United States House.”
Silver, a Michigan native, has become a celebrity of sorts since last Tuesday. He correctly predicted the outcomes of all 50 states plus the District of Columbia. In 2008, he called the outcomes of every state except Indiana, which narrowly went for Obama.