Conversation so far:
What is Chuck Bass' relationship with Blair Waldorf in Gossip Girl?
Blair Waldorf is Chuck Bass' main romantic interest throughout the series Gossip Girl.
Did Chuck Bass and Blair Waldorf begin a romance in Season 1 of Gossip Girl?
Despite Blair Waldorf losing her virginity to Chuck Bass, Nate and Blair rekindle their relationship.
Does Chuck Bass do anything bad during Season 1 of Gossip Girl?
In the pilot episode of Gossip Girl, Chuck Bass attempts to rape both Serena and Jenny Humphrey.

Question: What leads to his rift  with Blair and Nate?
Self-contained rewrite: What leads to Chuck Bass' rift with Blair and Nate in Season 1 of Gossip Girl?