A lot of poll watchers and race trackers have long noted that Rasmussen Reports seemed biased toward GOP candidates.
Now, the nation’s top political mathematician confirms it:
On Tuesday, polls conducted by the firm Rasmussen Reports – which released more than 100 surveys in the final three weeks of the campaign, including some commissioned under a subsidiary on behalf of Fox News – badly missed the margin in many states, and also exhibited a considerable bias toward Republican candidates. […]
The 105 polls released in Senate and gubernatorial races by Rasmussen Reports and its subsidiary, Pulse Opinion Research, missed the final margin between the candidates by 5.8 points, a considerably higher figure than that achieved by most other pollsters. Some 13 of its polls missed by 10 or more points, including one in the Hawaii Senate race that missed the final margin between the candidates by 40 points, the largest error ever recorded in a general election in FiveThirtyEight’s database, which includes all polls conducted since 1998.
Moreover, Rasmussen’s polls were quite biased, overestimating the standing of the Republican candidate by almost 4 points on average. In just 12 cases, Rasmussen’s polls overestimated the margin for the Democrat by 3 or more points. But it did so for the Republican candidate in 55 cases – that is, in more than half of the polls that it issued.
If one focused solely on the final poll issued by Rasmussen Reports or Pulse Opinion Research in each state – rather than including all polls within the three-week interval – it would not have made much difference. Their average error would be 5.7 points rather than 5.8, and their average bias 3.8 points rather than 3.9.
Nor did it make much difference whether the polls were branded as Rasmussen Reports surveys, or instead, were commissioned for Fox News by its subsidiary Pulse Opinion Research. (Both sets of surveys used an essentially identical methodology.) Polls branded as Rasmussen Reports missed by an average of 5.9 points and had a 3.9 point bias. The polls it commissioned on behalf of Fox News had a 5.1 point error, and a 3.6 point bias.
The analysis goes on and on, chronicling Rasmussen’s very atypical polling practices. Suffice it to say, Rasmussen runs a very shoddy polling firm.
We saw this in the gubernatorial race here. There were three independent polls taken in the final week of the campaign: Suffolk (7-point margin), WNEC (5-point margin), and Rasmussen (just a 2-point statistical dead heat).
So, just a cautionary tale for poll watchers here on RMG: you should either entirely discount Rasmussen Reports, or, at least, know that Rasmussen polls heavily bias toward GOP candidates.