A friend, Sarah Scanlon, just announced on facebook that she has been working with the Arkansas Voter Registration Project and they have registered over 60,000 voters in Arkansas over the last few months. This appears to be purposely unannounced until today. She says that these people would not be included in the polls. If 80% of these people vote and vote Democratic, it would give about a 6% swing to the Democrats in Arkansas (~780k people voted in 2010). That would probably be enough to give both Pryor and Ross a chance to win. She also says they have been knocking on 150,000 doors for GOTV. I guess we'll see if this work moved the needle.
5:36 PM PT: CNN called it for Cotton as the polls closed.