The most thoroughgoing dictators have avoided electoral danger by not holding elections at all, or by holding elections in which only approved candidates are allowed to stand — either just representing the ruling party, or sometimes including a token opposition as window-dressing.

Another strategy is to create a climate of repression and unfairness that is so pervasive it deters any credible opposition parties from emerging, or alternatively induces them to boycott the election in despair.

Failing that, autocrats resort to some combination of tactics to ensure victory regardless of any underlying popular sentiment. Common moves include using government-controlled media to deny publicity to the opposition; imposing onerous registration requirements on opposition candidates; engaging in pork-barrelling with government funds to buy votes; purging the electoral rolls of opponents or padding them with bogus loyalists; removing polling stations from areas of strong opposition support; appointing compliant electoral officials and preventing foreign monitors from observing the voting; jailing key opposition figures or threatening them with ruinous fines and other penalties.

If applied with sufficient ruthlessness, these tactics are usually effective. They work in places as varied as Egypt, Singapore and Belarus, and they worked in Zimbabwe for Robert Mugabe at the last presidential election, in 2002.

But sometimes misgovernment has been so flagrant, and the groundswell of opposition support is so strong, that all such measures fail to prevent defeat. An autocrat then has two alternatives: to go quietly, or to move to the next stage of ballot-rigging and nullify, falsify or simply ignore the result.

Even for a government in control of the electoral machinery, this sort of operation is much harder to pull off than the various pre-election shenanigans, if only because public scrutiny at the immediate post-election stage is so much more intense. Ferdinand Marcos tried it in 1986, and was swept away by popular indignation. The Burmese junta got away with it four years later, but at the price of becoming an international pariah.

Yet that is the choice that Mugabe now faces. It seems beyond doubt that lesser measures have failed and Zimbabwe’s people have voted to end his rule; the question is whether he will respect or defy that decision.

Winning an unfair election is one thing, but many leaders shrink from the next step of claiming a defeat as victory. Let’s hope Mugabe still has some scruples left.