A new SurveyUSA poll has Sen. Patty Murray (D) tied with Republican Dino Rossi at 47 percent, but the momentum is clearly in Rossi’s favor. Recent polling shows the Rossi’s numbers relatively unchanged, while Murray’s support is eroding:

Rasmussen (10/27): Murray 47 — Rossi 48

SurveyUSA (10/24-10/27): Murray 47 — Rossi 47

McLatchy/Marist (10/14-10/17): Murray 48 — Rossi 47

Public Policy Polling (10/14-10/16): Murray 49 — Rossi 47

SurveyUSA (10/11-10/14): Murray 50 — Rossi 47

This is not to say that Rossi’s support is static, but rather as more voters make up their minds heading into Election Day, it appears that the Republican challenger is simply outpacing the Democratic incumbent. If the current trajectory holds, Patty Murray (and the Democratic establishment) could be in for a real shocker.

A look at some key data from the latest poll:

• Among voters who say they have already returned their ballot (most voting in WA is done by mail) Rossi leads by two — 49 to 47 percent. Among voters who “promise to mail back the ballot but have not yet done so,” Murray leads by two — 46 to 44 percent.

• Rossi leads among independent voters, 50 to 40 percent.

• What age gap? Murray’s rally with President Obama at the University of Washington last week was a concerted attempt to bring out the youth vote for the Democrats. But did it work? Murray ‘s lead among voters aged 18-34 is just three points — 46 to 43 percent.

• Closing the gender gap. Murray’s lead among female voters has been as high as 17 points. It is now down to six.

• Among voters who said they were more enthusiastic than usual about voting this year, Rossi leads — 61 to 33 percent.

With only four days left to vote, these are not the sort of numbers any incumbent wants to see. Murray should be worried.

Update: Desperation in the air. From the PeopleforPatty Twitter account: “RT @alexjon: SurveyUSA shows Murray with strong advantage among those who haven’t voted yet, SO DO IT!”

A two point lead (46-44) among people who haven’t voted yet but “promise” to send their ballots in later is a “strong advantage?” For an 18-year incumbent? In a year like this? Let’s not get carried away.