The person who currently holds an office.
Incumbents usually win reelection: they're better known, have a record to point to and often raise more money. That's part of why open seats, with no incumbent running, draw so much attention.
"The incumbent senator is running for a third term."
Filed under government and law in the glossary, with every word used on How I Lean.
Nine questions, about three minutes, and you'll see where you lean.