As Murray-Rossi race gains importance, pollsters face challenges to predict it right

East Coast political observers increasingly think control of the U.S. Senate will hinge on who wins the contest between Democrat Sen. Patty Murray and Republican challenger Dino Rossi.

Nate Silver wrote a very interesting analysis today on the FiveThirtyEight blog of the New York Times that starts with the premise Washington is the tipping point state and tells why polling may not be giving an accurate picture of the race.

He writes:

The inconvenient thing about Washington State, however, is that the polling there has been all over the map.

Indeed, this has been a problem for some time. In April, one survey showed Mr. Rossi ahead by 10 points, while another had Ms. Murray ahead by 17.

Part of the problem, he surmises, is Washington’s vote-by-mail system can “wreak havoc with traditional likely voter models.”

Another interesting point he makes is that since 2000 the national polling firms, Rasmussen Reports and Survey USA, tended to overestimate Republican performance by 4 to 5 percent while Elway Research overestimated Democrat performance by 3 percent.

And those are the only ones doing consistent polling which means the best folks can is try to average out their findings.

There are several other points of why it’s hard to get a good read on Washington voters. It’s worth the time.