I honestly think all 3 of our men's qualifiers have a shot at a medal. What the top Kenyans and Ethiopians are doing these days is incredible, but the fact is that only 3 per nation get to the start line in Rio (plus a few others who have taken citizenship of other nations). And you never see all 3 from each country run a great race. 2012 E Mutai comes in with a 2:04 pr from London 2011, runs 10:00 slower. All 3 Ethiopians DNF. 2008 Luke Kibet DNFs. Plus leading up to the last 2 Olympics you had guys running super fast marathons just like now and not all of those runners could do the same in the Olympic Games.
Now, how much of a shot do I give the 3 US men... outside shot. Not long-shot, but certainly none of them get favorite status. Rupp debuted in 2:11 in hot conditions and didn't look pressed in LA. When he runs a marathon in more favorable conditions with international competition he's probably going to be 4-6 minutes faster than that. I think slow race or fast race he has the credentials (26:44/12:58) to race with the best in the world. He proved that to me on the track in London 2012. Then bring in the expected environmental factors in Rio, i.e. heat, and make it a 2:09-2:11 race and it's not a big stretch to me to see Rupp in the mix at 40k, on any given day hot/cool, fast/slow.
Meb and Ward I have different reasons to think they also have a chance to medal, but since this thread is about Rupp I'll hold those thoughts.