Senator Sampson was the incumbent and easily won yet another term.
John Smith, the presidential incumbent, had a great chance of being reelected.
The incumbent is demanding a recount.
The possessive form for the singular noun incumbent is incumbent's.
The incumbent is the current office holder, the "challanger' is the person running against the incumbent
The incumbent is the current holder of a political office. To vote "non-incumbent" would mean to vote for the challenger to the incumbent's position.
Barack Obama is the incumbent president.
Barack Obama is the incumbent democratic president.
The incumbent in an election is the current office-holder. For the 2012 Presidential race, the incumbent is Barack Obama.
an incumbent
An incumbent is an elected official who holds an office and is running for reelection.
the incumbent (your mom) the incumbent (your mom)
In politics, the incumbent is the person who holds the seat he/she is running for in order to keep it. The challenger is the person trying to win the seat that the incumbent has.