Terrorism and Election Outcomes

On March 11, 2004, terrorists set off a series of bombs on four trains in Madrid, Spain, killing 191 people and wounding 1,755.

In national elections held just three days later, the governing Popular Party lost to the Socialist Party. The outcome surprised many, especially since the last poll conducted ($ required) before the elections showed the Popular Party leading 42 percent to 38 percent.

The obvious conclusion was that voters changed their mind after the bombings. (One of the prevailing theories was that the Popular Party shot itself in the foot by intially pointing the finger at ETA, a Spanish separatist group.)

Yet opinion polls (pdf) conducted after the elections showed that Spanish voters felt the attacks had little or no effect on their vote.

But those polls were wrong, says Jose G. Montalvo, an economist at the Universitat Pompeu Fabra in Barcelona, Spain.

"We should trust only actual behaviour and not opinions in polls," he writes in a new paper.

To navigate around this, Montalvo got voting data from a group of Spanish citizens that were unaffected by the terrorist bombings: absentee voters living abroad. This group had to vote between March 2 and March 10, one day before the bombing.

Comparing historical data for both onshore and offshore voters, Montalvo extrapolates the results had there been no terrorist attack.

He concludes that the conservative party would have garnered between 42 percent and 45 percent of vote -- and won the election -- while the Socialist Party would have received about 37 percent of the vote.

Does this prove that timed terrorist attacks can influence elections?

Montalvo argues yes, but it's also probably more complicated than that. On the surface, it seems that a perfect confluence of factors may be necessary for an attack to have the intended consequence.

In the case of the Madrid bombings, the government was fighting an extremely unpopular war and the bombings, which the war had no small part in bringing about, was likely a catalyst that moved voters to oust the incumbents.