But on Friday, the well-respected Commission on Presidential Debates said that in fact, the Republican candidate was right.
"Regarding the first debate, there were issues regarding Donald Trump's audio that affected the sound level in the debate hall," the commission said on its website, without elaborating.
In that terse phrase the independent group thus confirmed that Trump was right in denouncing the quality of his microphone, even if his initial complaint was met with widespread derision and disbelief.
"They gave me a defective mic. Did you notice that?" he asked reporters after the debate, which was viewed by a record-breaking 84 million people in the US alone.
"My mic was defective within the room. I wonder, was that on purpose? Was that on purpose?"
It was not clear how much difference the technical problems might actually have made. Trump's words were at all times audible on the several networks that carried the debate, though at times there seemed to be a slight echo.
That might, however, have been distracting for the candidate, particularly one who seems to thrive on audience reactions.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)