Senate poll: Who to believe?

Last evening, A Survey USA poll done for KSTP showed Norm Coleman well out in front of Al Franken in the race for Minnesota’s U.S. Senate seat. On Saturday morning, a Minnesota Poll for the Star Tribune showed Al Franken well out in front of Norm Coleman for Minnesota’s U.S. Senate seat.

I know what you’re thinking: Something’s messed up here.

Over at MinnPost, politicos David Brauer and Eric Black parsed the two polls and found it appears to hinge on the Star Tribune’s practice of weighting the pool of respondents in favor of Democrats, figuring that more Democrats will vote in November than Republicans.

The Star Tribune poll involved more respondents contacted by a human on the telephone. Survey USA was a robopoll — an automated voice guides the person taking the poll.

Whose poll is more accurate? That’s the great thing about being a pollster. By the time someone checks your work, you’ve cashed the check and, besides, polling is just a snapshot in time. It’s not a projection.

But that won’t stop me from looking back and checking anyway.

In the last race for a U.S. Senate seat, the final Survey USA poll ( a day before Election Day) showed Amy Klobuchar ahead of Mark Kennedy 56-to-40 percent. She won 58-to-38 percent.

Conclusion? It was a heck of an accurate poll. The same poll, by the way, had Tim Pawlenty and Mike Hatch tied at 45%. And, indeed, when all was said and done, Mike Hatch lost by 1 percent of the votes cast.

A Star Tribune poll at the same time, had Klobuchar up 21 percent. Close, but not as close as Survey USA. (Updated: This is incorrect as David pointed out. Strib closer than Survey USA)

About 6 weeks before the election, Survey USA had Klobuchar up by 8 points, with Pawlenty and Hatch separated by 1 percent in favor of Pawlenty. Star Tribune had Klobuchar up 24 points.

So this isn’t the first time these two polls have been very different, but the current differences are unusually stark. The Democrats will say the Star Tribune is the accurate poll. Republicans, who’ve made a cottage industry out of assailing the Minnesota Poll in the past, will swear by the Survey USA poll.

As the saying goes, past performance is no indicator of future results. But where polling is concerned, it’s at least as good as any other guesswork that’s out there.