The abuses peaked in 2008, when Tsvangirai won more votes than Mugabe in the election's first round but withdrew from a runoff, saying he did not want anyone to be murdered for voting. About 200 of his supporters had already been killed.
Tsvangirai proved no match for Mugabe's wily political manoeuvering, which drew on his record as a leader in the struggle against white minority rule, his often violent intolerance of opposition, and his ability to marshal support from regional and broader African political forces.
Mugabe frequently inveighed against Britain, the former colonial power, and depicted his adversaries, including Tsvangirai, as puppets of the country's former imperial overlords.
When Tsvangirai became prime minister in 2009 under a power-sharing agreement brokered by neighbouring South Africa after the flawed vote of 2008, the pact and his new job diminished his ability to oppose the president.
Even as he accused Mugabe of flouting provisions of the unity government, many critics said Tsvangirai had been outwitted and co-opted by the president, his former sworn enemy. Indeed, Tsvangirai seemed to settle into a more comfortable relationship with him, built on the privileges of office.
In 2012, after Tsvangirai celebrated his second marriage with a glitzy party attended by guests arriving in Bentleys, Mercedes and BMWs, some of his followers were aghast at the ostentatiousness of the display and questioned who had paid for it.
By the time elections were held the following year, Tsvangirai was greatly weakened. He accused Mugabe of rigging the election and challenged him in the courts. But Mugabe claimed victory with 61 per cent of the vote, compared with 34 per cent for Tsvangirai, and it seemed that Tsvangirai's brush with high office was over. That was certainly Mugabe's view.
"We have thrown the enemy away like garbage," Mugabe said. "We say to them: You are never going to rise again."
For all that, Tsvangirai appeared in recent months to be attempting a comeback, even as he made frequent trips abroad for colon cancer treatment.
In 2017, he was part of a united front with other opposition groups, including the Zimbabwe People First movement, which is led by Joice Mujuru, a former vice president and onetime guerrilla fighter who was ousted by Mugabe in 2014.
"In 2013, we don't know what hit us," Tsvangirai said last year, finally conceding that he had been beaten in the polls that year. "We were defeated. But this time, we will refuse to be defeated."
The intention behind the alliance with Mujuru was to challenge Mugabe in elections in 2018, but that strategy was eclipsed by the military-backed intervention last November that brought Emmerson Mnangagwa, a former ally of Mugabe's, to power.
After Mugabe was overthrown, there was fevered speculation that Mnangagwa would seek a more inclusive form of rule than that of the leader he had just ousted. Instead, Mnangagwa lauded Mugabe and announced a government of his own supporters, including the military.
Even as he fell ill with cancer, however, Tsvangirai failed to groom a successor, and he left behind a fractured party with no obvious leader to challenge Mnangagwa in the elections expected this year.
The eldest in a family of nine, Tsvangirai was born on March 10, 1952, in the Gutu district of Masvingo province, in central Zimbabwe. The family was poor, and Tsvangirai abandoned formal schooling early to start work, first as a textile weaver and then as a plant foreman in a nickel mine.
Like Mugabe and Mnangagwa, Tsvangirai was a member of the dominant Shona ethnic group. But while they chose armed resistance from exile in the front-line states bordering what was then Rhodesia, Tsvangirai became a labour union leader, defending workers' rights and rising through the ranks. He was elected secretary-general of the Zimbabwe Congress of Trade Unions in 1988.
His political roots in the labour movement set him apart from those like Mugabe and Mnangagwa, who drew their legitimacy from the seven-year war against white minority rule. Initially an ally, he became a thorn in the side of Mugabe and his ZANU-PF party.
But as the president's intolerance became more evident, the gulf between the two men widened.