HARARE -- They are young, defiant and very excited.

"Viva viva!" they cry, in the powerful liberation chant of southern Africa, arms punching the air, glistening in the sweltering sun.

Pouring out of factories in the Workington district of Harare, they have come to see Morgan Tsvangirai at his final election rally, where everyone seems eager to choose him as Zimbabwe's next president.

"We all support him," supervisor Lameck Biri yells over deafening cheers. "Look at the notice board. It says 'Vote MDC.' "

Away from the cheers, Mr. Tsvangirai and his many supporters in the Movement for Democratic Change have a much less pleasing choice.

When voting ends tomorrow, on the opposition leader's 50th birthday, his nation will be at the brink. A rigged vote could unleash the sort of violence Zimbabwe has not seen since its independence struggle. A fair vote seems almost certain to give Mr. Tsvangirai a victory that his fierce rival, President Robert Mugabe, could try to crush.

But the opposition leader seems unfazed.

"Don't be accomplices to fear," he urges the crowd of 2,000 people who gather on a patch of wasteland grass. If the election is stolen there must not be violence, he says, urging his followers to take to the streets peacefully while his MDC challenges the result in court. "You know what to do," he says, as if he already knows this weekend's outcome.

And with good reason. Perched on the back of a truck with a portable microphone to address the masses, Mr. Tsvangirai and his MDC pose the greatest threat Mr. Mugabe has seen during 22 years in power.

The opposition leader has faced what he calls "intimidation on a massive scale."

Moments after his speech, we're speeding away in a motley motorcade of pickup trucks and Peugeots, ducking and diving down potholed side streets, passing each other and driving parallel to protect a presidential candidate who has grown used to the threat of death.

In bustling downtown Harare, where nerves are frayed but excitement is mounting, a packed truck and two cars pasted with Mr. Tsvangirai's face crawl down Nelson Mandela Avenue tooting. Grinning pedestrians offer the MDC's splayed-finger salute.

There is a singing crowd outside the party's nerve centre, named Harvest House in a country that was once a breadbasket but now has hundreds of thousands of people on the brink of starvation. Across the road, hundreds of people queue for maize rations.

Just three years after he founded the party, Mr. Tsvangirai, a former union organizer who started labouring in a textile factory when he was 20, knows he is destined to make history this weekend, for better or worse. Yet on the porch of his cream-coloured, middle-class house, he looks calm, even with burly security guards all around.

"It's my personality," he says as he flops into a wire chair for an interview. "When one goes into an experience like this, you have to develop a single-minded attitude, focusing on the objectives rather than the distractions. The objectives of democracy, economic recovery and improving the lives of Zimbabweans are totally motivating to me."

It seems like high talk for a man of the masses, but Mr. Tsvangirai has never been given to showmanship. He came to politics only after a long run in organized labour.

Two years after getting his first job, he found work at a nickel mine, was promoted to foreman and became active in the nation's largest labour group, which he later headed. By the late 1980s, the unions, once an important ally to Mr. Mugabe, had grown disenchanted with his corrupt rule and the massive failure of his socialist economic program.

In 1989, Mr. Tsvangirai spent six weeks in jail on allegations that he spied against Mr. Mugabe's government for the apartheid regime in South Africa.

Finally, in 1999, he launched an official political party after the Mugabe government crushed bread riots in Harare.

Mr. Tsvangirai's slow rise is partly the result of being too nice, as he is described by some colleagues. A few weeks ahead of the vote, he and two other MDC leaders were charged with treason, accused of involvement in a plot with a shadowy Canadian political consultancy to assassinate Mr. Mugabe.

The MDC vehemently denies the charges, but its members say Mr. Tsvangirai, who is often accused of being naive, should have walked out of a meeting with the alleged conspirators earlier.

"I will not be creating a Morgan Tsvangirai personality other than the one I enjoy and am confident about," he says. "But from now on people must earn my trust."

Despite Mr. Tsvangirai's disdain for Mr. Mugabe, the two men have more in common than they may care to admit. They share a disadvantaged background, single-mindedness and passion for Zimbabwe, as well as a history of populist struggle and a penchant for socialism.

While Mr. Mugabe casts back to an era of anti-imperialism and Marxism that finds little place in a globalizing world, Mr. Tsvangirai appears awake to world economic realities without abandoning what he considers the social imperatives of Africans.

He says a new government must get immediate food relief to starving citizens, turn around an economy in spiralling decline, restore the rule of law that Mr. Mugabe has abandoned in the face of growing political opposition and implement structured land reform in a country where state-sponsored invasions of white-owned commercial farms are destroying agriculture.

"I will also try to restore Zimbabwe's credibility in the eyes of the world, focusing globally on improving relations with Britain and the United States, which are economically crucial. And closer to home, on working with South Africa, Botswana and Mozambique," he said in the interview.

"Regionally, we will focus on bilateral relations with these three neighbours rather than multilateral relations, since the other countries of southern Africa have shown themselves to blindly favour the interests of Mr. Mugabe over those of Zimbabweans."

But he says the opposition must maintain an approach of non-violence, even if it loses the election. "Unlike ZANU-PF," Mr. Tsvangirai said, "we will have a non-violent approach to a stolen victory."