What is the total number of politicians whose predecessor's deputy is Jenny Macklin?
SELECT DISTINCT COUNT(?uri) WHERE { ?x <http://dbpedia.org/property/deputy> <http://dbpedia.org/resource/Jenny_Macklin> . ?uri <http://dbpedia.org/property/predecessor> ?x  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/OfficeHolder>}
Jenny_Macklin