Democrats can be very successful at the state level here -- they have the governorship and both Senate seats -- but the presidential vote has historically been much tougher to crack. The state has voted Democratic only twice in the last 50 years: The Lyndon Johnson landslide of 1964, and Bill Clinton narrowly winning its three electoral votes in 1992.
What's interesting to contemplate here is the role of effort. Democratic Senate candidates in Montana campaign in Montana. Democratic gubernatorial candidates in Montana campaign in Montana. I don't believe that Democratic presidential candidates typically do campaign in Montana. But Barack Obama has been putting some resources into the state. And there's long been a real question in my mind as to how much of the gap at the presidential level can be made up merely by showing up. Now that said there's a good reason Democrats don't normally campaign in Montana, which is that in addition to having a conservative track record it has very few electoral votes so it's hard to imagine it being the pivotal state.
But this kind of thing does have governance institutions. If Obama were to win the election, but lose Montana by the same 59-39 margin that Kerry faced, then Senators Baucus and Tester are going to take that into account when considering how supportive of Obama's legislative agenda they ought to be. If it's close, or if Obama wins, then they face a different calculation. That kind of thing is the significance of playing for the landslide.