How is the success of an interest group measured?

Whether the government changes its policy

Success can be reflected in the results

Explanation:

Interest groups, unlike political parties, do not want to be in power but to influence it and to contribute with their ideas. The interest group also generates public opinion and supports a certain candidate, political or any other in a dominant position.

The success of an interest group is reflected in its members, the more members the stronger the influence of the interest group will be. The interest group is lobbying, campaigning, seeking new people, convincing them that it is best option to support a particular person in politics, and thus if that candidate or person in a position in politics successfully rules a party or country it also represents the success of an interest group.