Donald Trump has said he does not support an age limit for running for president - but he does support a mental competency test. Trump, 77, told NBC News, in an interview to be broadcast on Sunday, that he thought age does not matter, but cognitive function does in a dig at Biden's brain function. Joe Biden, 80, is the oldest person ever elected president, and his age is worrying many voters across the political spectrum. If Trump wins, he would be 78 − the same age that Biden was when he began his first term in 2021. Biden and Trump are both out of step with the average American, who is aged 38.