I don't think this race has gotten enough exposure for an assessment to be made. If I remember correctly, neither has actually filed for the seat yet, and if they have it was very recently. I'll agree with the general consensus that Obama will help Trauner here, but Lummis will pull off a win.
Filing deadline was yesterday. The Republican candidates are Lummis, a rancher named Mark Gordon (who seems to be her only serious competition -- he's loaned himself $300k), a doctor named Michael Holland, and Bill Winney, who ran against Cubin in the 06 primary. Trauner is the only Democrat who filed. There's also a Libertarian.