Kay Hagan has been running a surprisingly close campaign against Thom Tillis, in spite of the fact that Hagan has done almost nothing of substance to distance herself from President Obama, who is broadly unpopular in North Carolina (and even more so if you accept the proposition that most everything Rasmussen does these days is garbage).
Tillis is facing his own popularity problems in North Carolina right now due mainly to the fact that the NC legislature, of which he is a prominent member (perhaps the most prominent member) has fallen on hard times in terms of public perception. However, tonight will present the first opportunity for Tillis to hang Obama around Hagan's neck on live television, and might well prove to be a turning point in the campaign. Importantly, this particular debate will air on all major local channels throughout the state on every network, ensuring that this will be much more heavily viewed in state than these affairs generally are. This presents a larger-than-normal window of opportunity for a turning point in the race.
Most of the television jousting promises to be a debate-by-proxy over who can associate their opponent most successfully with an unpopular third party. It will be interesting to see if either party is able to land a substantive blow about their own agenda specifically and how it would differ from the others'. For Tillis, this need seems less pressing since the fact that he is running even with the incumbent at this stage of the game in a sixth-year election already spells significant trouble for Hagan's chances.
For those who want to tune in live who don't live in North Carolina, C-SPAN will also air the debate and presumably stream it on their online properties.