I think Muskrat's chances of hanging on are well below 50% now. Remember that she barely held on in 2006.
This year she is facing an increasingly anti-GOP swarm from voters due to the economy as well as increased activity from various interest groups because this is a presidential election year.
There are far more boots on the ground canvassing, far more phone calls being made and far more literaure being delivered than what Musgrave faced in 2006. That increased field campaigning will probably be enough to push Betsey Markey past Musgrave on November 4th.