Mayor Giuliani built his reputation in New York on his brash, take-no-prisoners approach and his response to the World Trade Center attacks. As a presidential candidate, he’s wading into foreign policy matters more complicated than his bread and butter, dealing with terrorism.

Like several of his presidential rivals, Mr. Giuliani is adding his voice to the chorus of politicians and activists talking about the conflict in Darfur, where some estimate that 200,000 people have been killed since 2003 in what some term an ethnic cleansing campaign by the Sudanese government.

While it may seem counterintuitive for Mr. Giuliani, a leading Republican candidate, to take on an issue that’s been championed by many left-leaning activists and politicians, the conflict is of chief concern to conservative Christians and some pro-Israel Jewish groups.

Connie Mackey, the senior vice president at the political action arm of Focus on the Family, a Christian evangelical group, said Mr. Giuliani “needs to find a way to warm up to Christian conservatives, and this is an issue that they have taken to their hearts for years.”

Mr. Giuliani raised the issue at a fund-raiser last week, deep into his 38-minute address. He praised the Bush administration for focusing on Darfur, but called it to hold a summit for countries that can “help stem the tide of genocide.” A resolution of the conflict, he said, would demonstrate that “we can do positive things and good things.”

“We need to seize the opportunity to proclaim the heart and soul of what America is all about because we are allowing ourselves to be defined by our enemies,” Mr. Giuliani told about 1,000 supporters who were snacking on hot dogs.

The argument that getting more involved in Darfur would not only save Sudanese lives but also improve America’s worldwide reputation includes a national security angle. While he did not criticize Mr. Bush, suggesting that America’s image is tainted clearly distances him from the president.

Political analysts say Mr. Giuliani, who is surging in the polls, is creating that distance.

“It’s a high-wire act for Republicans,” a political science professor at the University of Virginia, Larry Sabato, said. “They have to be loyal to Bush on key policy issues to get the nomination, but they have to put some distance between themselves and Bush in order to win the general election.”

Ms. Mackey said she does not begrudge any candidate who brings attention to Darfur, but said Mr. Giuliani is searching for ways to bolster his foreign policy resume and make inroads with a conservative base that disagrees with him on gay rights, abortion, and other social issues.

The Giuliani campaign pointed to the mayor’s speech at the 2004 Republican convention, when he made a reference to “the slaughter of African Christians in Sudan,” to show that Darfur is an issue he’s been interested in for some time, not a cause he’s taken up to appeal to a slice of the electorate.

They also noted that the mayor discussed Darfur at a recent event with U2 front man Bono.

The vice president for government relations at the Heritage Foundation, Michael Franc, said Mr. Giuliani simply seems to be developing a more nuanced perspective of foreign policy. The senior advisor for international affairs at the American Jewish Congress, David Twersky, a contributor to The New York Sun, called Darfur “a big issue in the Jewish community.”

Presidential candidates from both sides of the aisle have spoken out on the issue. Senator Brownback, a staunch conservative, has been a leader, while Senator McCain teamed up with a former senator, Bob Dole, to write an opinion piece in the Washington Post calling for “U.S. and allied intelligence assets” to be used to document the killings.

Many Democratic presidential contenders, including Senators Clinton, Obama, Edwards, and Biden, have also been vocal, with some calling for no-fly zones and sanctions against the Sudanese government. Mr. Giuliani’s campaign did not say where he stood on those actions.