ISLAMABAD, Pakistan—Benazir Bhutto’s widower swept Pakistan’s presidential election on Saturday, offering hope for stability to a nuclear-armed country feeling intense U.S. pressure to crack down on Islamic militants.

In a grim reminder of the problems awaiting Asif Ali Zardari, rescuers in the northwest dug with their hands for survivors after at least 30 people were killed in a massive suicide bombing.

Already head of the main ruling party, Zardari becomes one of the most powerful civilian leaders in Pakistan’s turbulent 61-year history. Last month, he marshaled a coalition that forced stalwart U.S. ally Pervez Musharraf to quit as head of state.

However, he begins with limited goodwill among a population who recall his nickname, Mr. Ten Percent, for alleged corruption during Bhutto’s two terms in office as prime minister and doubt his political vision and leadership skills.

He is also untested on the international stage, where he must deal with mounting Western concern over how Taliban and al-Qaida militants have nested in the tribal belt along the Afghan border.

Secretary of State Condoleezza Rice said she was looking forward to working with Zardari.

“I’ve been impressed by some of the things he has said about the challenges that Pakistan faces, about the centrality of fighting terrorism, about the fact that the terrorism fight is Pakistan’s fight and also his very strong words of friendship and alliance with the United States,” Rice told reporters on a trip to North Africa.

Zardari made no mention of those topics as he savored his triumph over Musharraf, during whose reign he sat for years in jail on graft charges that never produced a conviction.

He was elected by members of federal and provincial parliaments. Official results gave Zardari more than two-thirds of the votes.