According to a review in the Guardian:
"Deronda was the first of Eliot's novels to be set in her own period, the late 19th century, and in it she took on what was a highly unusual contemporary theme: the position of Jews in British and European society and their likely prospects. The eponymous hero is an idealistic young aristocrat who comes to the rescue of a young Jewish woman and in his attempts to help her find her family is drawn steadily deeper into the Jewish community and the ferment of early Zionist politics.In the novel, the character named Mordecai is particularly interesting. Mordecai, according to the Guardian article is a "visionary intellectual." He is "a complex character with both sympathetic and unsympathetic sides and reveals a sometimes overwhelmingly detailed fascination with the minutiae of Judaism, its religious practices, culture and literature. The fact that Daniel becomes Mordecai's disciple and agrees to carry on his work to seek a homeland for the Jews after his death -- an idea presumably as baffling to Eliot's readers as it is to most of the book's gentile characters -- also shows a real commitment to the subject by the author."
"Their appearance in the book was as unwelcome to some of her readers as it is to some of the characters. While the novel's Lady Mallinger bemoans Daniel's 'going mad in this way about the Jews,' Eliot's friend John Blackwood noted upon publication: 'The Jews should be the most interesting people in the world, but even her magic pen cannot at once make them a popular element in a Novel.' Many years later, FR Leavis called for the Jewish sections of the novel to be cut out completely, leaving a country-house romance to be called Gwendolen Harleth, after the fatally self-absorbed gentile who falls for Deronda."