WASHINGTON — The Democratic and Republican presumptive presidential nominees are calling for the end of President Mugabe’s 28 years of rule in Zimbabwe if he moves forward, as expected, with a runoff election after driving his opposition out of the contest amid a wave of state-sponsored violence.

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Senator Obama said in a statement, “If fresh elections prove impossible, regional leaders backed by the international community should pursue an enforceable, negotiated political transition in Zimbabwe that would end repressive rule and enable genuine democracy to take root.”

Senator McCain floated the prospect of sending Zimbabwe’s diplomats in Washington home and suggested that the country be barred from participating in African regional forums if Mr. Mugabe clings to power.

“I believe the international community must act to impose sanctions against Mugabe and his cronies and thereby hasten the end of that regime. We should consider expelling Mugabe’s diplomats from Washington and explore options with our friends in Africa and beyond, including suspending Zimbabwe’s participation in regional organizations as long as Mugabe clings to power. The results of the March 29 election must form the basis of a post-Mugabe resolution in Zimbabwe,” Mr. McCain said.

The statements from the two major presidential candidates illustrate the bipartisan and international solidarity with Mr. Mugabe’s opposition leader, Morgan Tsvangirai, who is recognized to have won the March 29 elections in Zimbabwe. Mr. Mugabe prevented the official publication of the tallies from the ballots and promptly scheduled a re-vote for June 27. He also ordered a police and army crack down on Mr. Tsvangirai’s Movement for Democratic Change. Mr. McCain yesterday said that human rights monitors estimate that 60 opposition activists have been killed in the wave of violence, 2,000 have been tortured and “tens of thousands have been beaten.”

While neither candidate proposed military action against Zimbabwe or the arming of the democratic opposition, both are calling for the end or change of Mr. Mugabe’s regime. Mr. Obama said he spoke on the phone with Mr. Tsvangirai and expressed his concern for the treatment of his supporters. “The United States and the international community must be united, clear and unequivocal: the Government of Zimbabwe is illegitimate and lacks any credibility,” Mr. Obama said.

Mr. McCain indicated that the route to Mr. Mugabe’s ouster would be through sanction and censure, and that such measures should be implemented to “hasten the end of that regime.”

The re-emergence of regime change as a policy favored in the political cycle comes after that foreign policy goal in general had gone out of favor in Washington after the 2003 invasion of Iraq.

But until the lead up to the Iraq war, regime change was an option for both Democratic and Republican presidents. President Clinton pursued the extradition of the former Serbian despot, Slobodan Milosevic to a tribunal at the Hague following the NATO bombing campaign to prevent the Serb effort to cleanse of Kosovo of its Albanians. Mr. Clinton also signed, but did not implement, the Iraq Liberation Act, which made the end of Saddam Hussein’s regime a goal of American policy.

Zimbabwe presents a special case. Mr. Mugabe consented to the March 29 elections that both the British and American governments say Mr. Tsvangirai won. Also, Mr. Mugabe over the past seven years has sought to nationalize many of the remaining farms in the country owned by whites, plunging his already fragile economy into hyperinflation and depression. As his economy soured, he spurned offers from international aid organizations to meet basic needs of his people.

The tough rhetoric in Washington and London however do seem to have deterred Mr. Mugabe. Speaking to reporters in Harare, the 83-year-old president said, “We will proceed with our election, the verdict is our verdict. Other people can say what they want, but the elections are ours. We are a sovereign state, and that is it.”

One of the Mr. Mugabe’s few remaining allies, the South African government, also warned against any plans for regime change. The ruling party, the African National Congress, released a statement that said: “A lasting solution has to be led by the Zimbabweans and any attempts by outside players to impose regime change will merely deepen the crisis.”