First I will say that the vast majority of parallelism questions are testing structural parallelism (nouns with nouns, infinitives with infinitives, etc.) and only a small percentage deal with logical parallelism. The reverse is true for comparison questions as more comparison questions deal with the logical comparability instead of the structural comparability.
The GMAT is generally very straightforward in testing logical parallelism/comparisons. The wrong answers will definitely be illogical - making landfills parallel with pollution (Verbal #49) or comparing mammals with birds' tubes (OG #136).
In your incorrect example, from a meaning standpoint it is illogical because the intro phrase implies the meaning that it is his nomination that represents a step forward, not the politician himself. If written "The politician represents a step forward in urban-rural relations because he lives in the city but maintains and spends time in his childhood home in the country", the sentence would be more logical. That said, I believe the logical parallelism/comparison issues you will face on the GMAT will be much easier to discern.
Kyle Widdison | Manhattan GMAT Instructor | Utah
Manhattan GMAT Discount | Manhattan GMAT Course Reviews | View Instructor Profile