I should have realized the list below was a good way of generating a lot of “what about my guy?” inquiries. Obviously, flipping a seat requires a few ingredients: a strong challenging candidate, a mobilized grassroots, a couple of gaffes or unpopular stands on the part of the incumbent, strong or weak top-of-the-ticket candidates, sufficient fundraising, at least somewhat favorable demographics in the district, and a little bit of luck.
In the end, you can help your guy check some of those boxes.