American National Election Studies (ANES) surveys are done frequently and ask respondents whom they voted for, their party affiliation, and their opinions of political parties and their candidates. These surveys help political scientists .

Understand why people vote the way they do.

Explanation:

Political scientists frequently use political surveys, be it private or public (like the ANES) surveys, in order to ask voters for information such as  whom they voted for, their party affiliation, and their opinions of political parties and their candidates. With this information, they are able to form statistics which helps political parties see how they are doing, among other things.