As said before, the Teamster building helps you in the election. If they're bothering you, you'll have to take care of them- at one point or another. First off, try locating their office. Explore, and do it often. Try exploring areas in which you often see the opposing hoods, and sends a lot of people at once.
Kidnapping is another way of finding the enemy base.
To do this, you must find a building in which you often see the opposing hoods. Pulling this off will require a group of hoods that have high ratings in intelligence, intimidation, stealth, firearms, and organization. Succeed, and you will gain a list of businesses owned by the enemy. Investigate these buildings. Once you find the office, decide what you really want to do.