campaign has 15 distinct synonyms spread across 7 of its 7 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a race between candidates for elective office
“I managed his campaign for governor”
a series of actions advancing a principle or tending toward a particular end
“he supported populist campaigns”
several related operations aimed at achieving a particular goal (usually within geographical and temporal constraints)
an overland journey by hunters (especially in Africa)
run, stand, or compete for an office or a position
“Who's running for treasurer this year?”
Synonyms, antonyms and the broader and narrower relations for campaign come from Princeton University’s WordNet. Full sources and licences.