Given the following passage

"The People's Committees led to a high percentage of public involvement in decision making, within the limits permitted by the RCC, but exacerbated tribal divisions. They also served as a surveillance system, aiding the security services in locating individuals with views critical of the RCC, leading to the arrest of Ba'athists, Marxists and Islamists. Operating in a pyramid structure, the base form of these Committees were local working groups, who sent elected representatives to the district level, and from there to the national level, divided between the General People's Congress and the General People's Committee. Above these remained Gaddafi and the RCC, who remained responsible for all major decisions.",

answer the following question. Note that the answer is present within the text.

Question: What was the stepping stone that the committees used prior to being effective at a national level?
sent elected representatives to the district level
The passage explains the structure of Libya's People Committees. It mentions that "the base form" is local working groups, who send elected representatives to district level committees. Since this allows for representation at a national level, it can be inferred that this was the stepping stone in making these committees effective nationally.
So, sent elected representatives to the district level is our answer.