What was the imbalance in The Force in Phantom Menace?

In Episode 1, Mace Windu mentions the prophecy of the Chosen One who will bring back balance to the force. At that time it seemed like everything was going alright for the Jedi and the Republic, so what was the imbalance back then? Obviously by Episode 2 Palpatine had grown more powerful and was influencing events, but in Episode 1 things weren’t that bad. via /r/StarWars http://ift.tt/2AK2fC4