Being a mayor of a small town and being a US Senator or even House Rep are two very different things. It is very likely that, despite being Republican, he did nothing to further Republicanism with the power that he did have.
Most of the time, mayors really just do small town mayor shit like approving a tree to be cut down or asking the state for a road to be fixed. They’re not usually involved with politics in the way Lindsey fucking Graham is.