In 2010, I complained when Charlie Cook suggested that somehow public campaign polls were worse than the private polls shared mainly with reporters and observers like him. Cook wrote:
The far more sophisticated polling is done by top-notch professional polling firms for campaigns, parties and major business and labor organizations. These polls are considerably more expensive and the methodology is more rigorous.
Most of these surveys are not made public, but insiders can be made aware of them. While even the most experienced and contentious political pollsters have more challenges than a generation ago, their work is still far superior and reliable.
And I wrote:
I simply assume that campaign operatives, conscious of what Cook’s ratings might suggest about a race, would be happy to share private polls with him if they thought the poll results might move Cook’s ratings in a particular direction. I am not accusing Cook of anything at all; to me, his ratings have a lot of validity. I am merely making a statement about what campaign operatives do.
And now comes this:
Under oath, Hickman admitted that in the final weeks of Edwards’s 2008 bid, Hickman cherry-picked public polls to make the candidate seem viable, promoted surveys that Hickman considered unreliable, and sent e-mails to campaign aides, Edwards supporters and reporters which argued that the former senator was still in the hunt —even though Hickman had already told Edwards privately that he had no real chance of winning the Democratic nomination.
“They were pounding on me for positive information. You know, where is some good news we can share with people? We were monitoring all these polls and I was sending the ones that were most favorable because [campaign aides] wanted to share them with reporters,” Hickman testified on May 14 at the trial in Greensboro, N.C. “We were not finding very much good news and I was trying to give them what I could find.”
Hickman testified that when circulating the polls, he didn’t much care if they were accurate. “I didn’t necessarily take any of these as for—as you would say, for the truth of the matter. I took them more as something that could be used as propaganda for the campaign,” the veteran pollster said.
Like I said, no reason to believe that private polls are better or worse on methodological grounds, but every reason to believe that private pollsters will pick and choose which polls they share with you.