I am good at spotting people," George Butler has said. And indeed, it was the filmmaker-photographer's 1977 documentary, Pumping Iron, that introduced an obscure bodybuilder named Arnold Schwarzenegger. But if Arnold is Exhibit A, Exhibit A-plus is Butler's four-decade photographic project on John Kerry. After meeting him at a 1964 barbecue, Butler became a kind of Boswell with camera: joining Kerry on his first honeymoon, managing his first (unsuccessful) political campaign and shooting more than 6,000 photographs so far. This September Butler will release both a documentary and a book, John Kerry: A Portrait (Bulfinch Press). He is not an objective outsider, but his images provide a rare combination of chronological sweep and intimacy. TIME picked the following photographs from Butler's portfolio.