Some economists theorize that a long time Mayor of Boston (James Curley) used economic populism (taxing wealthy people of English descent and redistributing to poorer, usually of Irish descent) and anti-British rhetoric to reshape the electorate in ways that benefited him, even if it didn't benefit the city as a whole. The theory goes, he had a plan to drive out the wealthy people of English descent so the poor people of Irish descent would make up a larger share of the electorate and he could win more elections.

My understanding is that even most economists think that this isn't actually real. It's largely a couple of economists building a mathematical model, and then looking at cherry-picked examples, e.g., minority mayors during the 1970's and assuming that it was the result of a dastardly plan by the minority mayors rather than the result of larger social forces driving White Flight from cities.

In general, I think that mayors might make dumb decisions, but they largely do it because they think it will be good for the city and are wrong, not because they are twirling their mustache and cackling away.