Andreas Madestam and his team at Harvard found a way to check weather street protests are an effective mean of political change. In 2009 the Tea Party, an american conservative movement, organized huge protests gathering in total 450–800k people in 500 cities. In some of the cities the turnout was small due to rain. This was the foundation for the study. They calculated that rain lowered the attendance by about 60%. Using this finding they compared the influence of protests on the results of local elections. They calculated that one person that came to the protest mobilized on average 7-14 additional people to vote for the cause.
The study also shows that the larger gatherings caused an increase in the probability that a democratic member of congress will step down. They also caused politicians representing this electorate to vote on average more conservatively later on.