THE NEED FOR ENEMIES: Why politicians seeking re-election might never quite complete their key task

History is littered with politicians elected ''to get the job done'' who are then removed from office once they have delivered: think of Britain''s wartime leader Winston Churchill voted out soon after the war ended. According to research by Leopoldo Fergusson, James Robinson, Ragnar Torvik and Juan Vargas, this phenomenon means that there are strong incentives for politicians to avoid completing the key task for which they were first elected.

In a study published in the June 2016 Economic Journal, they explore how ''the need for enemies'' might encourage politicians to keep the task alive to maintain their advantage in future elections. In addition, the researchers produce robust empirical evidence that a ''need for enemies''-type logic shaped the counter-insurgency military efforts of President Álvaro Uribe during the 2000s in Colombia.

Uribe was elected in 2002 largely with the mandate of bringing the 40-year old internal armed conflict to an end by military means. Being himself a victim of FARC, one of the world''s oldest guerrilla groups (which had killed his father), Uribe was widely thought to be the man for the job.

During his tenure as president, Colombia''s government had a few extraordinary opportunities to secure an almost complete military victory over the guerrillas. The death of FARC''s chief ''Sureshot'', the killing of its deputy chief Raúl Reyes, and the rescue of internationally renowned politician Ingrid Betancourt, who had been abducted by FARC and kept prisoner for over five years, were all major hits against the insurgents, which led to mass desertions of demoralised troops.

As it turns out, just precisely after the events that created these windows of opportunity, the government''s military counter-insurgency efforts declined rather than increased. The researchers find that this decline was more prominent in places that were more electorally salient for incumbent president Uribe, when he was seeking re-election.

Their study notes that a job contract that makes employment conditional solely on completing a specific task creates incentives for an employee to avoid completing it by all means. By delivering, the employee would be putting him or herself out of the job.

This phenomenon may be particularly important in politics. It is often claimed that some politicians are elected because ''they are the person for the job''. But by getting ''the job'' done the politician would lose electoral support and probably be replaced, as salient policy issues will be likely to shift to areas in which other politicians would excel.

Winston Churchill was widely thought to be the prime minister who would lead Britain to victory in the Second World War. He did indeed get the job done but once the Allies had won, British voters replaced him with Clement Attlee, an arguably better peacetime politician. There are several other historical examples, in Britain and elsewhere, of politicians who, by getting the job done, are rewarded by being kicked out of office.

But there are also politicians who refrain from getting done the job they are elected for, thus making themselves needed for a longer period in office. Social anthropologist Frederick Bailey calls this phenomenon ''the need for enemies''. Sometimes ''enemies'' are needed to maintain power. Once the enemy is gone, a new enemy is likely to rise, but then the person for the job will be someone else.

The researchers demonstrate formally that a politician who is good at undertaking a particular task has an incentive not to complete it fully, since he or she needs to keep the task alive to maintain their strategic advantage in an election. This implies that when the opportunity is ripe to destroy the ''enemy'', politicians seeking re-election will not take advantage of such an opportunity.

Of course, for this to be the case, voters have to be responsive to policy outcomes. If people vote for non policy-related reasons, such as ideology, then the choices of politicians are of little electoral relevance, and the ''enemy'' is not necessary to begin with.

The need for enemies is not a universal law, the authors conclude:

''Even in cases in which politicians'' choices shape the voting behaviour of people, if the cost of keeping the enemy alive is too high, then the incentive to destroy it may offset any electoral ambition. In this case, the politician will deliver.

''In the example of Winston Churchill, keeping alive the Nazi threat and having the war continue were pretty high costs to pay.''

''The Need for Enemies'' by Leopoldo Fergusson, James Robinson, Ragnar Torvik and Juan Vargas is published in the June 2016 issue of the Economic Journal. Leopoldo Fergusson is at the Universidad de los Andes. James Robinson is at Harvard University. Ragnar Torvik is at the Norwegian University of Science and Technology. Juan Vargas is at the Universidad del Rosario.