Rep. Ken Buck (R-CO) tried to lob a political grenade Tuesday by demanding Vice President Kamala Harris bench President Joe Biden by invoking the 25th Amendment, but it may have exploded in his hand. “Biden no longer has the mental stamina needed to serve as president,” Buck wrote on X. “That’s why I’m urging the vice president and Cabinet to remove President Biden via the 25th amendment.” Buck cites special counsel Robert Hur’s report on his classified documents probe that accused the 81-year-old of being an “elderly man with a poor memory” and noted how Biden mixed up the president of Egypt …