Donna Edwards takes the nomination from Al Wynn. The significance is three-fold. On the one hand, Wynn was a bad rep and now he's gone, which is good. On the other hand, this is a very safe seat for Democrats, so a talented, principled representative like Edwards has the opportunity to use it as a base of operations to be a major progressive leader. It's very desirable to get these seats into the hands of people who'll be more than just reliable votes, but actually go the extra mile to really advance important causes. There's no telling if Edwards will live up to that promise, but she's an extremely impressive individual who certainly has the potential.
Last, the tree of progressive politics must be watered with the metaphorical blood of sellouts ever now and again. Some people seem to me to walk around in their head with a model in which politicians are very principled ideologues who then divert from their default status due to electoral fears. In a more plausible schematic, they have a natural tendency to drift in the direction of utter corruption and only electoral fear keeps them doing their jobs in a somewhat responsible manner. The demonstration effect of even a narrow win is large, and that of a substantial defeat like the one Wynn suffered can be very big indeed. Elected officials across the country are taking note.