Question: Under which US president was a politician in opposition of John G Schmitz?
SPARQL query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT ?uri WHERE { ?x prop:opponent <http://dbpedia.org/resource/John_G._Schmitz> . ?x onto:incumbent ?uri  . ?x rdf:type onto:Politician}