Trump gets name of his doctor wrong as he challenges Biden to cognitive test

Gaffe came as 78-year-old Republican presidential candidate sought to bolster his support among Black and Latino voters in Michigan

Donald Trump has made a point in recent months of deriding his rival Joe Biden as being cognitively impaired, mocking the 81-year-old US president for his verbal stumbles and accusing him of falling both up and down stairs.

But people in glass houses shouldn't throw stones.