To+every+thinking+person++At+summer+camp+in+Maine++The+Most+Outstanding+Camper++Was+Eat-it-all+Elaine!

What the author means by this is that everybody in the at the award ceremony was thinking that Elaine was the most outstanding camper. The award is not revealed in the poem, but even if Elaine does not win the most outstanding camper award everybody thinks that she is. The other campers like Elaine so much because she is very entertaining to them when she eats disgusting things that are not considered food.