any venturesome undertaking especially one with an uncertain outcome

exert oneself continuously, vigorously, or obtrusively to gain an end or engage in a crusade for a certain cause or person; be an advocate for

an organized program of advertisements

a campaign against entering or continuing a war

a campaign of flattery and friendliness (by a company, politician, etc.) to become more popular and gain support

a movement advocating greater protection of the interests of consumers

the campaign of a candidate to be elected