Thousands of people marched in the Philippine capital's financial district Wednesday, demanding the ouster of President Gloria Macapagal Arroyo, in the largest demonstration since she was accused last month of cheating in the 2004 election.

Although officials said the rally was smaller than the mass protests that toppled two previous Philippine presidents, including Arroyo's predecessor, Joseph Estrada, it gave new momentum to opposition efforts at forcing her from office.

Manila's police chief, Vidal Querol, told Philippine television that the turnout was no more than 15,000 people. Rally organizers, by contrast, said they exceeded their target of 50,000 and predicted even larger crowds at a series of upcoming protests designed to erode Arroyo's standing.

Police went on high alert ahead of the rally, citing possible terrorist threats, but it came off peacefully.

The protest, which closed the heart of the city's Makati area to traffic, attracted members of several opposition political parties and activists from student, worker, farmer and religious groups. By early afternoon, long columns of demonstrators waving multicolored banners and flags began marching past blocks of office towers toward a central stage, where political speeches alternated with blaring songs satirizing the president.

The rally was capped at nightfall by an emotional speech from Susan Roces, a former movie actress whose late husband, Fernando Poe Jr., was defeated by Arroyo in the disputed 2004 presidential contest. Poe died in December after a stroke.

"Our voices are tiny, but if they are joined together, they will be heard," Roces told the boisterous crowd. "Let us restore the honor of the Filipino people."

Apple Provido, 20, a psychology student, attended the demonstration with her parents, both activists in a government employees organization, to demand Arroyo's resignation.

"She's a liar, and she should not be the leader of the country. She's supposed to be a model, but she's not. She committed a sin," said Provido, citing the allegations of vote fraud while waving a red-and-yellow banner.

The demonstration was called by a group named the United Opposition. Some Arroyo opponents in the march urged that Vice President Noli de Castro take over as president, but scores of signs insisted that de Castro also step down. And several large red banners demanded: "All resign!"

Divisions within the opposition are one of the few encouraging signs for Arroyo, whose popularity continues to tumble. An opinion survey conducted this month by Pulse Asia Inc. and released this week found that 72 percent of respondents in the greater Manila area did not trust the president and that 68 percent disapproved of her performance.

The drive to force her from office appeared to slow last weekend, when the country's influential Catholic church announced it would not join the mounting calls for her resignation but instead urged that the allegations of wrongdoing be investigated.

Both Arroyo's supporters and detractors were preparing to decide her fate in Congress, which was scheduled to take up an impeachment motion in two weeks.

The showdown, coupled with a Supreme Court decision to block a proposed value-added tax increase, was taking a toll on the Philippines' struggling economy. Moody's Investors Service announced Wednesday that it was joining two other rating agencies in downgrading the Philippines' credit outlook. The Moody's rating went from stable to negative.

Thousands gather in the Makati financial district of Manila to call for the president to resign over allegations of fraud in the 2004 election. Protests toppled two previous Philippine presidents. President Gloria Macapagal Arroyo has denied wrongdoing.