Well, the media seems to often describe social conservatives such as Schuler or Ellsworth as just "conservative."
And Brown and Tester ran rather populist campaigns, not liberal campaigns overall, for example. I personally think Tester won in spite of some of his more liberal positions, rather than because of those positions which is what some crazy DailyKos'ers seem to think.
Tester being strongly against the Iraq War and the Patriot Act are really libertarian positions and fit in well with Montana (which is a libertarian state).
By the way, did anyone see Tester's victory speech? I want to see it bad.