Normally, I'm all for partisanship. There are, however, exceptions. The Washington Post's editorial about the District of Columbia's general election in November reminds us, for example, that there actually will be a general election in November. The outcome, however, isn't actually in doubt -- in this town, the Democratic primary just is the de facto election. As far as I can tell, there's no good reason to run a city with such a lopsided partisan balance this way. It would be much better to run non-partisan elections in two rounds. For the first round, anyone who got a certain number of signatures or whatever would be on the ballot. Then, if nobody got a majority, you'd have a runoff between the top two vote-getters in November.
That's not a perfect system (indeed, there is no system) but under the normally prevailing circumstances, it would be most likely to generate a reasonable outcome. The current system where you can win a Democratic primary with a plurality, and then enjoy a walkover victory in the general election, allows people to get elected mayor on the basis of what's potentially an extremely narrow base of support and means that whatever proportion of the DC electorate isn't registered as a Democrat gets essentially no voice in the governance of the city. Meanwhile, at this point very few major America cities (I think New York is the other big exception) still run partisan elections for local offices, so it's not like I'm putting some crazy notion forward here.
UPDATE: Some commenters are doubting my contention that New York and DC are exceptional in this regard. According to this article:
In more than 80 percent of the nation’s largest cities, mayors are elected through nonpartisan elections – elections in which the candidates do not run on the Democratic or Republican or any other established party line, but as individuals. The cities where there are non-partisan elections include Los Angeles, Chicago, Houston, Detroit, Denver, and San Francisco. New York City is the exception.
Boston, Philadelphia, New York, and DC, however, all have partisan elections which makes it seem like this is primarily a regional issue with the Northeastern cities generally having partisan elections and cities outside the Northeast generally opting for the non-partisan route.