Complex sentence: The Tanzim is a grass roots organization that operates at the community level and, by taking a hardline position toward Israel, it has helped siphon Palestinian support from the Islamist groups to the Palestinian Authority and PLO leadership.
Split into simpler sentences: The Tanzim is a grass roots organization that operates at the community level. By taking a hardline position against Israel, it has helped siphon Palestinian support from the Islamist groups to the Palestinian Authority and PLO leadership.