Barack Obama is the incumbent president.
An incumbent is an elected official who holds an office and is running for reelection.
A governor already in office.
The mayor who is in office and running for reelection.
An elected official who is running for another term in office.
opponent
The party who does not have a 'the' candidate in office, incumbent means that that parties candidate already holds the office.
An incumbent is someone already in a position or job. The doctor that you go to see is the incumbent, as opposed to a doctor you have not been to before. A doctor applying for an open position at a clinic would be a candidate.
The possessive form for the singular noun incumbent is incumbent's.
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
the incumbent (your mom) the incumbent (your mom)
An incumbent is an elected official who holds an office and is running for reelection.
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.