There are many reasons people choose to run for public office. Some of these are altruistic and based on a desire to genuinely make a difference while others are entirely ego-driven. All candidates should have a 25 word "I'm running because..." that articulates their public reasons for running. This is carefully crafted and is usually not the real reason a candidate is running. So why do people run?
Some candidates run because they feel slighted by their opponent or local government. These candidates tend to want to stick it to their opponents and want to immediately go negative. They have a vendetta against an official or an office and think the best way to fix the problem is by running for office. I had an African-American Congressional candidate who 3 months into the campaign sheepishly admitted to me that he had decided to run after meeting the incumbent and interpreting a LOOK he was given as being called the N-word. The word was never uttered by the incumbent, my candidate had merely interpreted a look to mean that. He was out for blood and took every opportunity to go after his opponent, even to his own detriment.
Many candidates choose to run to stoke their own ego, to be in the spotlight, and have people tell them how great they are. These candidates are running to be something rather than to do something. Many times this is about the perceived quality of life improvements associated with being an elected official. They want to make a bigger salary, or get rich becoming a lobbyist after their service. The title sounds nice to them and they think people will respect them more. These people tend to not care about the issues and only about making themselves look good. The most extreme examples are individuals whose egos are so large that they truly believe that they know better than everyone else and want to impose their will on others.
Some candidates choose the office they’re running for because they feel it is a race they can win. A Republican running for Mayor in a heavily Democratic, urban district will never win. Many times the candidate will realize that they race they WANT is unwinnable at the current time and instead choose to run for a position they know they are likely to win. If they ran for an office that no one pays attention to, like water board, they have a much higher likelihood of victory and it positions them for a better office later. Plus, in that instance they can realistically still make a difference in the community, even if it is not particularly glamorous.
Some candidates run because they legitimately want to change policy and make a difference in the lives of their constituents. These candidates are few and far between. It's important to set reasonable goals so that you don’t disappoint yourself and your supporters. To make a difference for people is a noble calling, but know that the system is stacked against you. It will be difficult to accomplish most of what you want to do, so make sure you are realistic about what can be accomplished.