I moderated a CD 5 Candidates debate at for the Ahwatukee Republican Women's group on Tuesday. I would guess estimate the crowd at about 100, and I tried to shake things up a bit to get the group off of their stump speech.
I think the size and quality of this field is an indication of how vulnerable the Democrats are perceived to be this year. There are six candidates in this race and at least three, and possibly four are actually credible.
You are seeing the same thing in CD 1 and CD 8. Large fields of credible Republicans facing vulnerable Democratic incumbents in swing districts. When the dust settles, I think that at least two of those districts will be occupied by Republicans.