Since when did MO and MT become competitive?
I do not really think Burns (R-MT) is in jeopardy. He was back when his approval ratings were mediocre, but now that he's net positive, the late tidal wave washing the Montana GOP away will probably not go high enough to knock him off. At this point, though, the race is unclear - his opponents all have name recognition below 20%, although they have some nice pedigrees, with one representing the conservative Choteau County.
Talent (R-MO) is in trouble, on the other hand. His opponent, State Auditor Claire McCaskill, is widely respected and has much higher approval ratings, although Talent's are still positive. Recent polls show the race tied or McCaskill slightly up. It should be a very interesting one.