(Excerpt from a "Chairs training guide" that I'm working on in my spare time.)
The mission of a political party in general is to push the platform into law. Everything else needs to happen in order to reach for that goal. We build our organizations in order to elect candidates in order to have those elected officials make decisions while in office that we support. To leave an elected official to make their own decisions without our input is ignoring our primary mission. To let decisions made that violate our principles and values go without being addressed is setting aside those principles and values in order to achieve some kind of "victory". The ONLY victory that we should consider worthwhile is improving the lives of the people who live in our communities.
Our platforms are written to articulate what our ideas are in order to achieve that victory. Candidates that agree with our principles and values, and agree to help push our ideas into law should be the candidates that we endorse and support during an election. Then we need to work just as hard to hold them accountable to the promise that they made when running with our endorsement.