Marshall: 136,052
Cunningham: 104,981
Many are predicting a much lower turnout based on most runoff turnouts. The Cunningham campaign has publicly estimated the turnout near 200K. The Asheville Citizen - Times has suggested 75K. But they aren't comparing apples to apples. They are looking at recent runoff elections that involved downticket races such as the State Education Superintendent.
When the runoff is for a Senate race at the top of the ticket(no presidential primary) the turnout is much closer to the turnout of the primary.
The top-vote-getter in a Senate primary usually retains 90%+ of the primary vote. The runner-up is the wild card. In these runoffs, the runner up may get less than 50% of their original vote or more than 150%.
425,343 voted in the NC Dem 2010 primary. 154,605 voted for Marshall. 115,851 voted for Cunningham. NC is still very much in recession, so fundraising is tight. So I think that Marshall will fare a little worse than 90% retention. I think that Cunningham will get just over 100K votes because that's what they think they need to win.