This is a great question and one that desparately needs to be answered. I belive it begins with the public sending the message they are tired of the tactics being used in politics today. The message not only needs to be sent to each of the candidates who use these tactics it must gain exposure in all media sources of information.
The media today is also part of the problem in that they highlight the missteps of political candidates forgetting that every individual makes mistakes. The focus on politics today needs to be on the issues and how one candidate's position differs from the approach of their opponent or opponents. Focusing on how a candidate will attack the problems our country faces is what the public is looking for in a candidate. Negative ads while they may get some exposure they do nothing to instill confidence in any candidate.
Approaches by candidates needs to also identify what they would do differently in specific areas where policies have failed. All this needs to presented in a civil manner. Candidates may not agree on approaches to issues of the past or issues facing our country today but they must take the attitude of agreeing to disagree. This is the kind of message the public must send candidates for all levels of government.