Domestic issues trumped foreign policy in recent weeks on the presidential campaign as casualties dropped in Iraq and the situation calmed elsewhere in the world.
But today's assassination of former Prime Minister Benazir Bhutto in Pakistan, a front-line US ally in the war on terror, could change that dynamic, a week before the Iowa caucuses.
The candidates are starting to weigh in on the death of Bhutto, a pro-democracy opposition leader. Republican Rudy Giuliani, who has staked much of his candidacy on being tough on terrorism, was among the first to respond.
"The assassination of Benazir Bhutto is a tragic event for Pakistan and for democracy in Pakistan," he said in a statement. "Her murderers must be brought to justice and Pakistan must continue the path back to democracy and the rule of law. 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."
Republican Mike Huckabee called Bhutto's killing "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."
Mitt Romney, campaigning this morning in Nashua, N.H., told reporters that the attack on Bhutto was a reminder of the "extraordinary reality of global, violent, radical Jihadism."
"We don't know who is responsible for this attack, but there's no question but that the violence that we see throughout the world is violence which is not limited to Iraq and Afghanistan, but is more global in nature," Romney said. "And this type of loss of life points out again the need for our nation and other civilized nations of the West and of the Muslim world to come together to support moderate Islamic leaders and moderate Islamic people and to help them in their effort to reject the violent and the extreme. The world is very much at risk by virtue of these radical, violent extremists, and we must come together in an effort, in great haste and with great earnestness to help overcome the threat of the spread of radical, violent jihad."
Democrat Barack Obama, campaigning today in Iowa, said he was shocked and saddened by Bhutto's death.
"She was a respected and resilient advocate for democracy, for the people of Pakistan," he told reporters. "We mourn her loss. Our thoughts and prayers are with her family and her supporters, and we want to make clear that we stand with the people of Pakistan in their quest for democracy and against the terrorists who threaten the common security of the world.
"We'll be finding out more information as the day and the weeks unfold about this difficult situation," he added. "But we have to make sure that we are clear as Americans that we stand for democracy and that we will be steadfast in our desire to end the kind of terrorist acts that have blighted not just Pakistan but other parts of the world."
Democrat Bill Richardson, also campaigning in Iowa, called on Pakistani President Pervez Musharraf to step down.
"Benazir Bhutto was a courageous woman," Richardson said in a statement. "Her death, and the deaths of so many of her supporters, is more than just a tragedy. It is a testament to the will of the Pakistani people to see democracy restored...
"Ms. Bhutto knew the dangers to her safety. But she would not be intimidated. We also must not be intimidated. 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.
"We must use our diplomatic leverage and force the enemies of democracy to yield: President Bush should press Musharraf to step aside, and a broad-based coalition government, consisting of all the democratic parties, should be formed immediately. Until this happens, we should suspend military aid to the Pakistani government. Free and fair elections must also be held as soon as possible.
"It is in the interests of the US that there be a democratic Pakistan that relentlessly hunts down terrorists. Musharraf has failed, and his attempts to cling to power are destabilizing his country. He must go."
Republican John McCain noted that Musharraf has also survived assassination attempts.
"We're going to have to to devote a lot of effort to make sure things don't unravel in that country," he said while campaigning in Iowa.
Democrat Hillary Clinton, speaking at a high school in Lawton, Iowa, praised Bhutto's courage and placed her death in the broader fight against extremism.
"With the assassination of Benazir Bhutto today, the world once again is reminded of the dangers facing those who pursue democracy and free elections in Pakistan and elsewhere, in areas that are rife with conflict and violence and extremism and anti-democratic forces at work," she said.
"I have known Benazir Bhutto for a dozen years, and I knew her as a leader, I knew her as someone who was willing to takes risks to pursue democracy on behalf of the people of Pakistan. I grieve for her family, particularly her two children, and I grieve for people of Pakistan, who deserve to have the opportunity to vote for leaders of their choosing....
If there is any opportunity for the government and people of Pakistan to respond to this tragedy appropriately, it would be move more steadfastly and determinedly to democracy. She has given her life for that hope and I know that the people of our country stand in solidarity with those who believe as we do in the rights of people to be heard at the ballot box."
Democrat Chris Dodd, who said he has kept in touch with Bhutto over the past few weeks, cast the assassination as playing to his strength as a 26-year member of the Senate Foreign Relations Committee.
"As we recognize the loss of a leader today, we must also recognize the implication of today's tragedy to the security of the region and to that of the United States," he said in a statement. "At this critical time we must do everything in our power to help Pakistan continue the path toward democracy and full elections. Our first priority must be to ensure stability in this critical nuclear state.
"The United States should also stand ready to provide assistance in investigating this heinous act. And as Pakistan perpetrators to justice, it should also demonstrate that it will not allow such violence to derail democracy and proceed with elections in a timely manner."
Democrat John Edwards vowed to continue to help Pakistan's transition to democracy.
"Benazir Bhutto was a brave and historic leader for Pakistan," he said in a statement. "Her assassination is a sad and solemn event, and our hearts go out to her family and to the Pakistani people. But we will not let this contemptible, cowardly act delay the march of progress in Pakistan for a single second.
"I have seen firsthand in Pakistan, and in meetings with Prime Minister Bhutto and President Musharraf, the instability of the country and the complexity of the challenges they face. At this critical moment, America must convey both strength and principle. We should do everything in our power to help bring the perpetrators of this heinous act to justice and to ensure that Bhutto's movement toward democracy continues."
Democrat Joe Biden said that he twice had urged Musharraf to increase security for Bhutto and that her death "raises a lot of hard questions for the government and security services that must be answered."
Biden also praised Bhutto's courage and said he was convinced that she would have won "free and fair" elections in Pakistan. "The fact that she was by far Pakistan's most popular leader underscores the fact that there is a vast, moderate majority in Pakistan that must have a clear voice in the system," he said in a statement. "Her assassination makes it all the more urgent that Pakistan return to a democratic path."