Complex sentence: Congress was broadly divided between a faction supporting the policies of George Washington's administration and a faction opposed to those policies, although the Federalist Party and the Democratic-Republican Party were starting to emerge as distinct political parties in the First Party System.
Split into simpler sentences: Congress was broadly divided between a Pro-Administration faction supporting the policies of George Washington's administration and an Anti-Administration faction opposed to those policies. Due to this, the Federalist Party and the Democratic-Republican Party were starting to emerge as the distinct political parties of the First Party System.