Many years ago, i read a sic fi novel that i would really like to find again; i do not remember the title. The premise of the book was that aliens (known as the Watchers) were present on Earth and intervening in human affairs. There was an old man named Mordecai, a Jew, who had played in old vaudeville shows. I don't remember too much more; I will add it in if I do. The zeitgeist of this novel had such an interesting texture that it is memorable, even though the author and title escapes me. The book may have been from the 50s or 60s; I read it probably in the early to mid 70s. Thanks for any help.