CAIRO -- Support for Egypt’s Islamist political parties has plummeted ahead of this country’s presidential election next week, a Gallup survey released Friday has found, while early returns showed the candidate of the Muslim Brotherhood, thought to be Egypt’s dominant political group, running third among Egyptians voting overseas.

Both the poll and the early election results are the first authoritative measure of the state of Egyptian politics just days before the country’s first truly contested presidential election. Taken together, they suggest the grip that the Muslim Brotherhood has seemed have had on Egypt’s political system has loosened, giving liberals and Christians hope of avoiding an Islamist sweep of the new government.

The Gallup poll, conducted April 8-15, found that support for the Muslim Brotherhood had fallen from 43 percent in February, a month after the organization won nearly half the seats in Egypt’s Parliament, to 26 percent last month. Disappointment in the way Parliament performed probably drove that number. A separate question found that while 46 percent of Egyptians said in February that the new constitution should be written by the largest political bloc in Parliament, only 27 percent still felt that way in April.

And while 62 percent believed a Parliament with a strong Muslim Brotherhood showing was a “good thing” in February, by April, 47 percent said it was a bad thing.

Those polled also wanted to take powers away from Parliament. In February, 46 percent wanted Parliament to appoint the next prime minister, compared with 27 percent who favored the appointment being made by the new president. By April, the numbers had flipped, with 44 percent saying they now wanted the new president to pick the prime minister, compared with 27 percent favoring a parliamentary appointment.

With Egypt’s constitution still unwritten, it is uncertain how Parliament and the new president will resolve the issue.

Salafists, ultraconservative Islamists who once were aligned with the Brotherhood and make up the Parliament’s second largest bloc, also lost support. Their Nour Party lost 10 percent of its support from February to April, dropping to a 30 percent approval rate.

Many Egyptians have voiced disappointment with the Muslim Brotherhood in recent weeks, blaming it for Parliament’s lack of legislative accomplishments and its unwillingness to confront the country’s ruling military council on key issues. Many Egyptians also have criticized the Brotherhood for fielding a presidential candidate after announcing that it would not.

The Brotherhood’s dominance of the committee charged with writing a new constitution also may have contributed to the slide in its popularity. Many Egyptians have complained that the Brotherhood’s appointment of its own to the committee indicated that it was seeking to dominate the country’s political scene, rather than act in the national interest.

“They are not properly aligned with the demands on the street,” said Ibrahim el Houdaiby, senior researcher at the House of Wisdom, an independent Cairo-based think tank.

The Brotherhood has acknowledged its falling popularity but has blamed it on a biased news media and a public that doesn’t understand the limitations of the legislative process. Brotherhood officials have said that the group decided to offer a presidential candidate only after it realized the legislative process alone would not lead to real reforms.