The main aim of the political party is to gain power by supporting a candidate during election and the aim of the interest group is to have similar idea and to infuence public.
Explanation:
The main goal of the political party is to take a hold on the government whereas the goal of the interest party is to control the government.
political parties pursue their agenda through elections and the interest groups pursue the agenda through political process such as lobbying
political parties mainly focuses on general policies so that they can win majority of votes whereas in case of interest groups they specialize in one of the two policy areas.
In case of political parties platforms are placed in the middle of the road so that thy can attract masses and in case of interest groups they donate on campagn groups to influence people.