The death of former Pakistan Prime Minister Benazir Bhutto, after a suicide attack Thursday, prompted comments of sadness and a demand for justice from political leaders and presidential candidates.

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"Her murderers must be brought to justice, and Pakistan must continue the path back to democracy and the rule of law," Giuliani said in a statement. "Her death is a reminder that terrorism anywhere -- whether in New York, London, Tel-Aviv or Rawalpindi -- is an enemy of freedom. We must redouble our efforts to win the terrorists' war on us."

Sen. John McCain, R-Ariz., in a statement, said the death of Bhutto "underscores yet again the grave dangers we face in the world today and particularly in countries like Pakistan, where the forces of moderation are arrayed in a fierce battle against those who embrace violent Islamic extremism.

"Given Pakistan's strategic location, the international terrorist groups that operate from its soil, and its nuclear arsenal, the future of that country has deep implications for the security of the United States and its allies. America must stand on the right side of this ongoing struggle," he said, noting that he has made numerous visits to Pakistan.

Former Massachusetts Gov. Mitt Romney focused on the threat of "global, violent radical jihadism."

"This type of loss of life points out again the need for our nation and other civilized nations of the West and Muslim world to come together to support moderate Islamic leaders and moderate Islamic people to help them in their effort to reject the violence and the extreme," Romney told reporters after his first campaign event at Norton's Classic Cafe, in Hudson, N.H. "The world is very much at risk by virtue of these radical, violent extremists and we must come together, in great haste and great earnestness, to help overcome the threat of the spread of radical, violent jihad."

Democratic candidates also lamented Bhutto's death.

At a high school in Lawton, Iowa, on Thursday, Sen. Hillary Clinton, D-N.Y., said she had come to know Bhutto during the former prime minister's years in office and her time in exile and was "profoundly saddened and outraged" by the assassination.

In a world of such violence and threats, Clinton said, "it certainly raises the stakes high for what we expect from our next president. I know from a lifetime of working to make change."

Sen. Barack Obama, D-Ill., said he was shocked and saddened by Bhutto's death.

"She was a respected and resilient advocate for the democratic aspirations of the Pakistani people. We join with them in mourning her loss, and stand with them in their quest for democracy and against the terrorists who threaten the common security of the world," he said.

New Mexico Gov. Bill Richardson, a former U.S. ambassador to the United Nations, called on President George W. Bush to force Musharraf to step down. Until then, Richardson said the U.S. must suspend military aid to the Pakistani government.

"A leader has died, but democracy must live. The United States government cannot stand by and allow Pakistan's return to democracy to be derailed or delayed by violence," Richardson said.

The Bush administration has pushed hard for peaceful elections in Pakistan, a U.S. ally in the anti-terrorism war.

Bhutto was killed in an attack on an election rally in Rawalpindi. At least 20 others were killed in the blast that took place as Bhutto left the rally where she addressed thousands of supporters in her campaign for Jan. 8 parliamentary elections.

Bhutto served twice as Pakistan's prime minister between 1988 and 1996. She had returned to Pakistan from an eight-year exile Oct. 18. Her homecoming parade in Karachi was also targeted by a suicide attacker, and more than 140 people were killed. On that occasion she narrowly escaped injury.

Republican candidate Mike Huckabee called the turn of events "devastating news for the people of Pakistan, and my prayers go out to them."

"The terrible violence surrounding Pakistan's upcoming election stands in stark contrast to the peaceful transition of power that we embrace in our country through our Constitution," Huckabee said in a statement. "On this sad day, we are reminded that while our democracy has flaws, it stands as a shining beacon of hope for nations and people around the world who seek peace and opportunity through self-government."