Connecticut: More House Effects

Our Slate Senate Scorecard update for tonight focuses on a new Rasmussen poll in Connecticut that shows Joe Lieberman leading Democratic nominee Ned Lamont by ten points (50% to 40%).

Tracking the Connecticut Senate race especially challenging because the most active pollsters in the state have shown consistent differences in their results -- at least until today. See the chart below (courtesy Charles Franklin), which shows Lieberman's margin over Lamont (Lieberman's percentage minus Lamont's percentage):

Both the Rasmussen automated surveys and the conventional, live interviewer phone polls conducted by Quinnipiac University showed Lieberman's margins narrowing since July but holding fairly steady over the last month. However, until the survey released today, the Rasmussen surveys have consistently shown a closer margin than the Quinnipiac Polls. This pattern is similar to the one we described yesterday in Tennessee, where Democrat Harold Ford is running stronger on the Rasmussen surveys than on conventional telephone interview polls conducted by Mason Dixon.

In this case it is harder to use the survey mode (live interviewer vs. automation) to explain the differences in because the house effects are inconsistent by mode. Another live interview pollster (American Research Group) has also shown a consistently closer race, while automated pollster SurveyUSA reported Lieberman ahead by 13 points in early September.

Today's result, however, brings the Rasmussen and Quinnipiac polls into agreement, at least for the moment. The last Quinnipiac poll released last week also showed Lieberman leading by 10 points. So is the latest turn in the Rasmussen trend line the sign of new Lieberman momentum, a convergence in the polls results or just an outlier result? Only time, and more surveys, will tell for sure.