Which of the following have the greatest impact in determining and shaping public policy - political parties or interest groups? Be sure to explain your reasoning and support your answer with at least one example.

Question

anonymous · Answer

I believe it's political parties...

anonymous · Answer

Interest groups are groups that focus on people with specific needs such as senior citizens, women..etc. While political party is more of a national group who nominate candidates for certain positions. 
Am i close? Can someone explain further, please?