How are political parties and intreast groups similar

Similarities between political parties and interest groups:

The political parties and interest group join for a political reason. If the interest group wants the government to act on a particular issue they join hands with the people and also draw the attention of the political party towards to sort the issue.

Any group or individual if wants to influence on the legislature is the special interest groups. The interest groups, mainly act on the core issues that has to be addressed like capital punishment, abortion and all important social issues.

Though they cannot highly influence on the judicial process but puts an effort to influence them politically.  So they both try to influence the outcomes of elections and legislation.