He finally acknowledged the corn and admitted he was wrong.
acknowledge the corn
idiomTo admit to the truth of the point at issue or to a mistake; to cop a plea; or perhaps to admit to a small error but not a larger one.
Origin
first recorded 19th c. disputed originAn American expression. Its origin is usually explained via the punch line to some humorous story, but the story and the literal meaning of the punch line vary greatly. * In a debate on tariffs in the U.S. Congress in 1828, Rep. Stewart of Pennsylvania claims that Indiana, Kentucky, and Ohio exported corn to Pennsylvania; on being challenged by Rep. Wickliffe of Kentucky, Stewart explains that the corn to which he alluded is exported in the interiors of hogs fed on that corn. Wickliffe replies contritely, "I acknowledge the corn." * A Louisiana gambler, while drunk, wagers and loses a large quantity of corn and potatoes; when the winner comes to collect, the gambler says, "I acknowledge the corn, but the potatoes you can't have!" * A New Englander boasts of their fine corn fields; a Western visitor says "That's nothing! I'll send you some of our seven-foot corn." He does so, and receives a grudging telegram in reply: "I acknowledge the corn." * A drinker is accused of having imbibed too much corn whisky. He retorts, "I acknowledge the corn," implicitly refusing to acknowledge the "whisky" part of the accusation. In actual usage, though, the phrase was usually associated with drunkenness, which suggests the last of these explanations ("corn" as synecdoche for "corn whisky") is probably closest to the true origin.
After the evidence proved his mistake, he had no choice but to acknowledge the corn in front of his colleagues.
Although he initially attempted to deflect the blame, he eventually acknowledged the corn, conceding that his oversight had indeed caused the project to fail.