Still, you raise a good point, Chris. However, the reason I stated Senator Klobuchar’s (net) flat approval rating “suggests” she isn’t winning new converts, or losing her voting base is because we can’t know for sure, for two reasons:

1) The SurveyUSA poll is conducted among 600 Minnesota residents, not likely voters. More than 1 in 5 adult Minnesotans did not vote last November, so the pollster is likely picking up a fair share of that demographic in its respondents. Thus the poll isn’t entirely reflective of how the views of Minnesota *voters* may be changing.

2) The partisan splits can frequently vary quite wildly among a poll sample of this size (600). Any time you analyze the trends in the poll’s subgroups, in this case partisanship, the margin of error is much greater than when studying the sample as a whole (+/- 4.0 percent). The reason is simple: the number of Republicans surveyed, for example, amount to approximately 175 out of the 600 adults polled. This can lead to big changes from month-to-month, as it can on the Democratic side. For example, in the case of this pollster, the percentage of Minnesotans who identified as Democrats went from 33 percent in December 2008 to 44 percent in January 2009. That’s a 33 percent rise in 30 days, and partially a product of the larger margin of error that results from studying subgroups of this size.

While there are surely some unhappy folks with Klobuchar who voted for her on the Democratic side and some Republicans who voted against her that approve of her job performance, the main point is these folks have largely canceled each other out, and her numbers are flat.