query: SELECT ?item ?itemLabel ?party ?district ?districtLabel ?start ?end
  WHERE 
  {
    ?item p:P39 ?statement .
    ?statement ps:P39 [ wdt:P279* wd:Q16556694 ]; pq:P2937 wd:Q3522615 .
    OPTIONAL { ?statement pq:P580 ?start }
    OPTIONAL { ?statement pq:P582 ?end }
    OPTIONAL { ?statement pq:P768 ?district }
    OPTIONAL { ?statement pq:P4100 ?party }
    SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
  }
  ORDER BY ?districtLabel ?itemLabel