It has since been pointed out to me that Kepner's actions may have violated more than just tradition. He might have violated Richardson's Code of Ethics, which states that it is the policy of the City "that the City Council at all times shall be maintained as a nonpartisan body." The City Council cannot remain a nonpartisan body if its members are free to campaign in a nakedly politically partisan manner.
Kepner might claim that the city policy is an unenforceable violation of his Constitutional right of free speech. If the City agrees with that argument, the Code of Ethics ought to be repealed and replaced. Alternatively, if the Code of Ethics is enforceable, the City Council ought to censure Kepner for turning the City Council into a partisan body. There is no third option here.