Let’s get back to basics. Politician is a hired professional, selected by the majority of voting taxpayers to represent their interests in the particular government office. As the electoral machine requires significant resources, the politicians are usually assembled in gangs (parties), that have the ways to establish the channels of funds, offered at the condition that the party members will protect the interests of those who had paid.
I would define the politician to be decent if he represents the interests of the vast majority of those who elected him and at least a significant percentage of those who did not vote for him.
It is hard to ask that the politician represents every single person who voted for him, as many people do not properly link their interests to their electoral activity.