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3 November 2012

Flathead Memo October polling average has Tester leading by 0.7 percent

Update, 5 November. Flathead Memo calculates the odds Tester is leading are 3:2.

Six of the eight October polls of Montana’s 2012 U.S. Senate election reported Jon Tester leading Denny Rehberg by one or two points. One, the 14 October Rasmussen poll, reported a 48–48 percent tie. And one, the 31 October Mason-Dixon commissioned by the Lee newspapers, reports Rehberg leading by four points, 49–45 percent.

Flathead Memo’s average of the eight polls has Tester leading 46.7–46.0 percent, That’s a functional tie.

The Mason-Dixon poll may be an outlier. Tester’s campaign certainly thinks so. Earlier today it released a statement reading in part:

Tomorrow, Montana newspapers owned by Lee Enterprises are expected to release their own polling results of Montana’s U.S. Senate race. The newspapers use the firm Mason-Dixon Polling and Research. Mason-Dixon conducted a U.S. Senate poll in early October that many, including Montanans for Tester, consider to be inaccurate. [The Ravalli Republic in Hamilton published the poll today.]

Tester’s campaign may be right, but it did not provide supporting evidence and arguments. Moreover, this close to the election, statements from campaigns are self-serving, are intended to hearten campaign staff and volunteers, and thus, to put it as gently as I can, should be taken with a grain of salt. One can, however, infer from the data presented here that Mason-Dixon’s results may be at variance with the Tester campaign’s internal tracking polls.

Below are two graphs. The first displays the 2012 polls beginning in September, reporting the margin of error, the probability of Tester’s having a ballot lead, and the October mean. The second displays a high resolution look at Tester’s lead over Rehberg (in this graph, a lead can be a negative number).

Excel spreadsheet of polls in graphs below.