I'll put money on Murray and give Smiley a +4% in the spread. While the people hoping to oust Murray are very vocal and pointing out some things that need to change, the establishment there isn't having it. And while it's true that Smiley gained ground, it was a pretty vast separation that she dug into. Kind of like when Beto cut into Ted's lead a few years ago. My guess is that the new Trafalgar will show Murray with +2 in the coming days.
That sounds about right. The political climate strongly favors the GOP, and Smiley is a respectable candidate. However, Washington is pretty blue, and it has reliably elected Murray since 1992. Very hard to imagine them ousting her. Dino Rossi gave her a decent challenge in 2010, and he couldn't knock her off in a big Republican year. I think the Beta comparison is pretty good.
I will say this. If she does defeat Murray, the Democrats are in serious trouble. They aren't winning any of the even somewhat competitive races.