Precinct straddling of city boundaries

Suppose a situation in which citizens of a particular city vote in county, state and national elections, but in which their combined vote for each candidate is not clearly separable from the votes of residents of adjacent areas outside of the city. It can be argued that the inability to identify the city vote would have undesirable implications for the visibility of the political preferences of the people of the city, for the reliability and indeed validity of the process of administering city elections and for the accessibility of the city to analysis of its political history.