Question

Political parties must convince voters that their candidate and ________ best represent the voters' political beliefs and interests.

Answer 1

I'm not really sure what your options here are, and I couldn't find them anywhere on the Internet. However, I will try to help you if I can. 
It is important for political parties to persuade their voters that their candidates and the ideas they stand for will be for the best of those voters. They need to show the voters that the candidate will fight for their rights and for giving them what they want in order to persuade them to vote for that particular candidate and the entire party.