Science is defined usually as either a learning discipline, pursuit of knowledge, or a body of knowledge based on observations and/or experiments. Politics or political science is the study of different political systems and behavior as well as its effects on a community.
There is a large difference between a "soft science" and "not a science". Social science is especially difficult because it is nearly impossible to control for every variable. This does not make it not a science, it merely makes it a less accurate one.
It depends. Positivist social scientists tend to be more scientific in that they readily utilize the scientific method in their work. Interpretivist social scientists are not really scientific. Ideology also plays a huge part in some SS fields, making them much less objective, too.