Brayden King, a professed expert on the issue, says they do:
Our model demonstrates that protests matter by drawing attention to issues and sustaining a public discussion about that issue, which in turn forces Congress to pay more attention to the issue. But to be successful in shaping the agenda, an issue must receive more protest treatment than other issues do. Protestors are actually competing with other protestors for agenda space.
2006-2011 archives for The Daily Dish, featuring Andrew Sullivan