Even if a politician who told the truth, the whole truth, etc. did get elected, she would soon become part of the political system, and in order to survive would have to fit the system. The system is sure a large part of the problem.

Another part of the problem, which I've mentioned repeatedly here and elsewhere is the voter. I strongly believe that no one should be allowed to vote unless they can demonstrate at least a basic knowledge of our political system, issues on which candidates are running, etc. Across-the-board enfranchisement means that people whose idea of society comes from reality TV have the same say in elections that professors of political science have.