Martin O’Malley, the nearly forgotten third candidate in the Democratic primary contest, is not going to win Iowa’s caucuses. But he could have a meaningful impact on the outcome.

The reason: Democrats require their candidates to meet a certain threshold of support in each caucus, usually set at 15% of caucus-goers, in order to compete. A candidate who doesn’t meet the threshold is deemed “not viable.’’ His or her supporters can either sit out the caucus or throw their support to a viable candidate.

One other alternative: One of the viable campaigns could send a few supporters over to the vote-starved candidate in order to allow him or her to survive.