According to a new Public Policy Polling survey, Sen. Patty Murray leads Dino Rossi by two points — 47 to 49 percent — among likely voters. The result is virtually unchanged from an indentical poll taken in July, which had Murray leading 49 to 46 percent. PPP calls the race “the most stable in the country”:

The reason for the stability is that voters know these candidates, they know what they think of them, and nothing they’ve heard during this campaign has changed those opinions in one direction or the other. In July Murray’s approval rating was 46/45. Now it’s 47/48. In July Rossi’s favorability was 43/48. Now it’s 44/49. This is a race where persuasion means little and everything will hinge on who bothers to cast their ballots in the next few weeks.

Barack Obama won Washington state by 17 points in 2008, but this year’s likely voters supported him by only seven percentage points. The candidates’ support breaks down on largely partisan lines. Murray is winning 93 percent of Democrats, while Rossi is getting 91 percent of Republicans. Among Independents, Rossi leads 49 to 43 percent.

The race is difficult to poll because of the prevalence of mail voting in the state, which has already begun — 14 percent of those surveyed had already cast their ballots, and supported Murray by a margin of 52 to 47 percent. The race is going to come down to who decides to vote, and will likely keep a lot of us up late on Election Day.