Why is effective campaigning important during elections?

Effective campaigning is generally effective because the campaigner persuades a population to support him. During an election, the one objective a candidate has is to win; the candidate wins an election by gaining the most support from the population. So effective campaigning is important because it gives the candidate with the campaign a greater chance of winning the election.

This is assuming the targeted population votes for a candidate in an election, not all types of government hold elections that would require a campaign.