Sponsoring an add-on event
The SunTrust Richmond Marathon, in Richmond VA, has added a half-marathon (to go along with its 8k) and sold title sponsorship to McDonald's.
The McDonald's Half-Marathon, as it will be called, taps into the fastest growing distance in road racing and hopes to swell the field by offering a challenging distance for runners who aren't interested in, nor ready for, a marathon.
On the plus side, McDonald's has a reputation for being an active sponsor, doing more than just posting signs everywhere. Its resources can, evidently, jump start a new event and contribute to its growth.
However, many runners may refer to the race as the Richmond Marathon, the Richmond Half-, or the half- at the Richmond Marathon. Race organizers will have to find ways to encourage and reinforce use of the McDonald's name (and SunTrust, too).
If McDonald's is replaced by a different sponsor in the future, the race will be given a new name. That should not be a problem, though, because it's an add-on to an existing event. The name is less important than it would be for a stand-alone race.