I think protests work if there is already a critical or near-critical mass of support in the relevant decision-making body (legislature, courts, civil service, etc.) Protests rarely change minds, but they can give already-sympathetic people a new impetus to take action in this area rather than another.
ETA: It also helps if the protesters have specific, focused demands, like “end segregation,” or “bring the troops home.”
I think protests work if there is already a critical or near-critical mass of support in the relevant decision-making body (legislature, courts, civil service, etc.) Protests rarely change minds, but they can give already-sympathetic people a new impetus to take action in this area rather than another.
ETA: It also helps if the protesters have specific, focused demands, like “end segregation,” or “bring the troops home.”