I take exception to Rabbi Lewis’ answer to a question where he stated that Samaritans are not Jewish. In 1842, the Chief Rabbi of Eretz Yisrael, Haim Gaggin, and the Bet Din in Jerusalem, stated categorically that "the Samaritans were a branch of the House of Israel". I interpret that to mean that they have been recognized as Jews for the last 160 years.
In the Tanach Kings 2 17; 24-31 the origin of the Samaritans is from tribes brought over by the Assyrian kings and they are not Jews. See also Ezra 4;2. The Rambam holds them as non Jews and in a way even worse. (Commentary on Mishna Brachot 8; 8) Rabbi Eshtori HaParchi in his book Kaftor VaFerach follows the path the Rambam went. The term "A branch of the house of Israel" given by the Chief Rabbi of Jerusalem Rabbi Avraham Chaim Gaggin does not mean at all they are Jews but that their belief in the five books of Moshe (though they twist it a lot) and in one G-d binds them in a way with the Jews, it's a politically correct way of saying they are not Jews… More so though I'm no authority in Jewish history, it seems like this statement was given only to save the Samaritans from genocide by the Muslims of the time and such a statement of the chief Rabbi could protect them from being wiped out. Bottom line is the Samaritans were and remain non Jews and that is the official approach of Halachic Judaism today.