Which seat did Tester represent? It's possible that the seat only went Native-held in 2006. Then again, he was certainly *born* in Havre, which is in a whitewashed district neighboring a Native-majority one.
I'm not sure what his seats nor am I familiar with the Montana state Senate map, though Tester is from Chouteau County after looking it up...so probably not after all. If it includes Hill and Blaine counties than it makes sense though, you have a district where the Democrats heavily rely on the Native vote but they don't make a majority and can't elect their own. Much like blacks in all the white Democrat-held seats in Georgia and North Carolina.
Yah, the area is cut up to have a Native Senator and a White Senator:
SD 8 (HD 15 & 16), SD 16 (HD 31 & 32) and SD 21 (HD 41 & 42) are the Native Districts.
Oh, and the new Representative of HD 15 is Mr Frosty Calf Boss Ribs.
And while I was at it, I also checked what District Tester represented: SD 15 (that area elected a Democrat? Wtf? Currently it's delegation is all-Republican again. Excluding the portion of Chouteau, and including the portion of McCone not in the district, McCain took 67% here. Also, the district is just 0.9% Native American.)