Which of the following best defines the term 'incumbent'?

The term 'incumbent' is best defined as a person currently holding an elected public office. This definition is important in the context of elections and political processes, as incumbents often have certain advantages over challengers, such as name recognition, established constituent relationships, and experience in the role they are serving. Incumbents are individuals who are presently serving in their position and are often running for re-election.

The other choices refer to different roles or states within the political arena: a person campaigning for office is typically a challenger who seeks to take the position from the incumbent; a former public office holder has completed their term and is not currently in office; and a local government employee may not hold an elected position at all, but rather a staff position within the municipality. Understanding the definition of 'incumbent' is crucial for anyone studying political processes and elections, as it highlights the dynamic of ongoing political roles versus those who are seeking to displace them.