KARACHI, Pakistan — Benazir Bhutto made a dramatic return to Pakistan today, ending eight years of exile to reclaim a share of power with the country’s American-backed military leader. More than 150,00 jubilant supporters gathered to greet her amid massive security.

Ms. Bhutto, who is expected to seek the premiership for an unprecedented third time and partner in ruling Pakistan with American-backed President Musharraf, was in tears as she descended the steps of a commercial flight that brought her from Dubai to Karachi, where jubilant crowds of flag-waving, drum-thumping supporters waited to give her a rousing welcome.

“I counted the hours, I counted the minutes and the seconds, just to see this land, to see the grass, to see the sky. I feel so emotionally overwhelmed,” Ms. Bhutto, who wore a white headscarf and clutched prayer beads in her right hand, said.

“And I hope that I can live up to the great expectations which people here have,” she said.

She said she was fighting for democracy and to help this nuclear-armed country of 160 million people defeat the extremism that gave it the reputation as a hotbed of international terrorism.

“That’s not the real image of Pakistan. The people that you see outside are the real image of Pakistan. These are the decent and hardworking middle-classes and working classes of Pakistan who want to be empowered so they can build a moderate, modern nation,”

Ms. Bhutto, 54, fled Pakistan in the face of corruption charges in 1999. It would take a constitutional amendment for her to be prime minister again; Pakistani law bars leaders from seeking a third term.

Authorities have mounted a massive security operation to protect her from possible attack by militants. But the precautions failed to dampen the spirit of huge crowds forming in Karachi.

Hundreds of buses and other vehicles festooned with billboards welcoming her back were parked bumper-to-bumper along the boulevard from the airport to the city center. A huge red, green, and black flag of her Pakistan People’s Party hung from one apartment block overlooking the route.

Supporters including representatives of Pakistan’s minority Christian and Hindu communities and Baluch tribesmen with flowing white turbans, walked toward the airport, while groups of men performed traditional dances, beat drums or shook maracas along the way.

A 35-year-old poultry farmer from the southern city of Hyderabad, Azad Bhatti, said he had “blind faith” in Bhutto’s leadership.

“When Benazir Bhutto is in power there is no bomb blast because she provides jobs and there is no frustration among the people,” he said. “Whatever she thinks is for the betterment of the people.”

Ms. Bhutto paved her route back in negotiations with General Musharraf, who seized power in a 1999 coup. General Musharraf, whose popularity has waned as violence by Islamic radicals has risen, is promising to give up his command of Pakistan’s powerful army if he secures a new term as president.

The talks have yielded an amnesty covering the corruption cases that made Ms. Bhutto leave Pakistan in the first place, and could see the archrivals eventually team up to fight Al Qaeda and the Taliban.

Prime Minister Shaukat Aziz welcomed Ms. Bhutto’s return, saying it would improve the political and help democracy to “flourish.”

But General Musharraf, who had urged Ms. Bhutto to delay while he dealt with legal challenges to his continued rule, stayed silent, and a government spokesman claimed her rally was a flop.

“It is the PPP workers’ response and not the public response and even the workers’ response is much less than what she was expecting,” Information Minister Muhammad Ali Durrani said.

The crowd seemed far smaller than the 3 million Ms. Bhutto claimed had turned out to welcome her. Its size was estimated at 150,000, strung along a four-mile stretch of the road, a senior provincial official said. He spoke on condition of anonymity because he is not authorized to release the estimates.

Still, the gathering was larger than most of her rivals could hope to muster, and it showed that Ms. Bhutto’s party machinery remained intact despite her absence.

A White House spokeswoman, Dana Perino, declined to comment directly on Ms. Bhutto’s return but said America wanted “a peaceful, democratic Pakistan, an Islamic state that is a moderate force in the region, and one that can be an ally to help us fight extremism and radicalism.”