Right now I have ads from both John Barrow and Doug Haines who are both competing to be the nominee in Georgia's 12th.
In a different political climate - say, one, in which Dems controlled the Senate and it wasn't a presidential election year - I would have thought that becoming actively involved in some primary races would be quite a useful thing to do. If your party doesn't have an incumbent in the race, then it's during primary season when you have a good opportunity to influence who the candidate - and hopefully the eventual congressperson - is. For those who are concerned about the lack of progressive Democrats in Congress, it's a chance to get them in there. Prove they can win the primary, prove they can raise some money on their own - then the institutional support money comes raining down on them.
But, it wasn't something I spent any time on this year so I really have no opinion about any of the contested primaries. However, if you think either candidate is the kind of person we need in Congress I suggest you lend your support. This is a seat that we "should win," given party registration numbers, so there's a reasonable chance that whoever wins the primary will win the race.
