This use case is usually handled via {leaflet}, which is built on Open Street Map tiles rather than Google Maps data. The reason being that Google is rather unfriendly in their Terms & Conditions, while OSM is open data in its purest form.
What country's electoral districts are you interested in? If the Czech Republic I could share with you some code handling the use case - I am about to teach a course on VŠE in early February on spatial data and I have prepared some scripts using the results of the October elections. Especially Středočeský kraj makes a great fodder for spatial data analysis, as there were two popular mayors (Líbeznice & Mnichovice) leading two major parties.
I will be open sourcing the materials after the course is concluded, but I suppose no harm would be done in discussing it privately (you may have an idea how to improve the course, if I am lucky).