Leading article: Even amid the horror, an election is still the best way to oust this tyrant

The benighted country of Zimbabwe has entered the last days of campaigning before next Friday's poll. As recently as a week ago it was hard to imagine how the circumstances of this presidential run-off could possibly deteriorate any further. Yet deteriorate they have, with practically every day bringing new evidence of the depths to which Robert Mugabe is prepared to stoop to hang on to the dismal remnants of his power.

The opposition leader, Morgan Tsvangirai, is spending the weekend closeted with senior members of the Movement for Democratic Change, considering – not for the first time – whether to go on. While the prospects were always slim that the poll would be anything like free or fair, the deviousness of the stratagems employed by the Mugabe government and the ruthlessness with which his henchmen have pursued members of the opposition have exceeded the most pessimistic predictions.

The campaign has been marked by escalating physical cruelty. The government clearly calculated that the relative calm in which the first round was conducted acted against its interests. The notorious veterans' militias have been mobilised in rural areas, where the opposition did unexpectedly well in March. Individuals suspected of sympathies with the MDC have been kidnapped and beaten. The wife of Harare's mayor became the fourth mayor's wife to be abducted and killed. Many thousands have been forced to leave their homes, thereby forfeiting their registration, and their vote.

Campaigning, for the opposition, has been so hedged about with restrictions as to be almost meaningless. MDC rallies are banned for spurious reasons of security; its campaign adverts are rejected by the monopoly state broadcaster, ZBC. The party's secretary general has been arrested and charged with treason. And while the authorities have – so far – stopped short of charging Mr Tsvangirai himself, he has been arrested several times while out campaigning.

Even international food aid has become a weapon in the government's hands. Regions that vote for the MDC have been threatened with having their aid withheld. In a country where up to half the population could run short of food in the coming year, this is a particularly base – and effective – form of blackmail.

All this – designed to deter, if not actually destroy, the opposition – is before any voting has actually begun. If and when it does, the old tricks of siting polling stations in the middle of nowhere, manipulating the electoral lists, and stuffing and mislaying ballot boxes will doubtless come into play. That such techniques failed to prevent the MDC's win in March was largely thanks to assiduous monitoring by local party activists and observers, who meticulously recorded the actual vote tallies, station by station, as they were posted up.

It is not at all certain that there will be such effective monitoring this time. The level of intimidation is much higher, and the number of observers has been slashed. It seems that there will be only 500 domestic monitors – almost 20 times fewer than in March – along with 500 from other African countries.

With so much stacked against him, and physical danger ever present, it would be understandable if Mr Tsvangirai withdrew. Why should he give Mr Mugabe the satisfaction of an electoral "victory"? Having come so far and braved so much, however, he has no reason to accept defeat. Beset by inflation and food shortages, Zimbabweans voted for change once; they might be courageous enough to do so again. Nor, with a handful of African leaders starting to question Mr Mugabe's rule, is the MDC quite as friendless as it was. Even at this late stage, it would be wrong to abandon hope.