Since the early days of the 2020 presidential campaign, quiet speculation has swirled about Joe Biden’s mental fitness for office. Now, eight months into his term, that quiet speculation has turned into serious doubt about the judgment of President Joe Biden. A history of plagiarism, gaffes, and informal anecdotes that proved untrue has now combined with serious questions about cognitive decline — all suggesting that someone other than Joe Biden is pulling the strings at the White House. Doug McKelway reports.