There are a few clients who require special rules, based either on class or experience. Politicians and political parties are a very special case.
Due to the nature of campaigns- cash is tight, the demands are high and timelines short, and they tend to fold up shop the night of the election (if not sooner)- the wise ask for half up front and the balance before the product is handed over. This means literally holding a tape hostage until you have payment, ideally something that acts like cash.
An audio friend of mine once had to keep the podium mic at a live event turned off until he had cash in hand. The candidate was about 20 feet from the stage, about to speak to the crowd, before the envelope appeared. The mic was turned on, the event was great, the client was happy, and later apologized for the drama. Had my friend not held the line, odds were high that he would have been stiffed. Campaigns have little loyalty to their vendors.
I once spent a day shooting for a Presidential candidate who eventually stiffed my boss. The candidate dropped out of the race before our invoice got paid. That's a hard way to make a donation to a campaign, especially if you are not a supporter.
Trust most, but some just have to pay cash.