Phoenix is a city whose time has come. The inner city is being restored, the university is moving downtown, and property values are on the rise. But we haven't quite arrived. Any downtown metropolis worth its salt has a commuter rail system. Just look at New York, Chicago, Seattle, and San Francisco. Don't leave Phoenix behind. Vote "Yes" for light rail.

Explain how the argument illustrates the bandwagon fallacy and why that fallacy makes the argument weak.

The bandwagon fallacy is  in the insistence that good cities are good because they have rail.

Explanation:

The bandwagon fallacy is where the causation of something is confused as an effect. It is the argument that because all the great cities of the country have light rail, our city too should have the same light rail system to be as good as them.

This argument falls apart because the rail will not curb the problems that the passage itself talks about and then willfully ignores. In fact, bringing the rail to town will actually aggravate some of the issues mentioned here. Which is why the argument becomes more weak.