The Teamsters Union is "technically" a membership organization, but in reality it is a hollow organization, run mostly by a nationwide insider group of officers and stewards. On those rare occasions when contracts are voted on, information and discussion is kept to a minimum, and the officers usually endorse the Contract unanimously and pressure all stewards to follow suit. The Contract is deliberately negotiated so it has just enough sweeteners to satisfy the (high-seniority) stewards and those who are close to the stewards and influenced by them. Most Contract criticisms and shortcomings are never heard, except where TDU has a presence. The vote is often rushed, and the Company makes it seem like a "No" vote is a vote to STRIKE!!! and destroy out livelihood. Some people are ineligible to vote, and many others are turned off. Only a small percent of the whole bargaining unit actually votes, and many of the "Yes" votes are probably stewards, alternates, and friends thereof.
Richard Milhous Nixon won by the biggest landslide in history, but after Watergate, it was hard to find anyone who would admit to voting for him.