actually Flake is my sleeper pick to have problems in both primary and general. He won AZ by just 5 points in the 2012 election despite Romney winning Arizona by 10. This was for a GOP held seat and it was an open seat but still. Flake had been a House member. So actually I think Jeffry has more problems than just a primary. He's probably facing in the midterms the same type of electorate that he faced in 2012 (where he didn't clear a majority of the electorate, by the way).
He can / will probably win but I am also saying it might be close in both.
I don't think that's a sleeper pick - Flake is not an electable guy.