Some candidates win but disappoint their supporters and even themselves. They achieve little or nothing of what they hoped to do. Here are incumbents' worst mistakes:
Hiring staff who don't personally share their policy agendas. Personnel is policy. Staff who lack enthusiasm for their bosses' priorities prevent elected officials from doing what they intended to do in office.
Not keeping campaign promises. These days voters have little tolerance for incumbents who break their word.
Not paying attention to the interests of the coalition which elected them. Incumbents lose their allies when they don't vote right, sponsor key legislation or sign allies' fundraising letters and aren't there when their friends need them.
Seeking approval of their enemies, particularly their media enemies. Many incumbents start craving to have everyone love them and no one hate them. But trying to make friends of their enemies makes enemies of their friends.
Failure to handle constituent relations effectively. All politics is personal. Service can be as important to voters as policy. They appreciate prompt, personal service when they contact those elected to serve them.
Succumbing to temptations newly present when one achieves some power. Election to office tests anyone's strength of character, family ties and personal morality.
Getting greedy for money or higher office.
Becoming arrogant. Many people, constituents who request help and especially the officials' staff, treat incumbents with deference bordering on obsequiousness. A consequent loss of humility can destroy a politician's base.
Accommodating opposition incumbents who now are "distinguished colleagues." Excessive collegiality is a trap for incumbents who really want to accomplish things.
Not helping to nominate and elect allies in their home states and elsewhere. A well-run team takes care of its own. Serious politicians work hard to elect others who share their public policy principles.