CAIRO - The Muslim Brotherhood has deployed a formidable campaign machine in its quest for the Egyptian presidency but faces an uphill struggle winning over voters, hampered by its own image problems and the limited appeal of its candidate, Mohamed Mursi.

A 60-year-old engineer, Mursi has at times appeared ill at ease in the public eye since he was thrust into the race by the disqualification of the Brotherhood's primary candidate, Khairat al-Shater. Mursi's critics say he lacks charisma.

The movement to which he belongs is meanwhile trying to fix a broader image problem. It is facing tough criticism from other Egyptians over its handling of the 14 months of military rule that followed Hosni Mubarak's downfall.

After prayers on Friday, Brotherhood activists deployed outside one Cairo mosque to hand out Mursi campaign pamphlets, accompanied by a leaflet trying to debunk accusations leveled against the group, including the idea it has broken its promises to Egyptians by seeking to monopolise public life.

"We see that our popularity has fallen a bit," said Essam Khalil, a Brotherhood organiser at one campaign event. "But we are on our way to recovering it," he said.

"We have a group of activities going into the street: meeting the people; holding meetings and marches and showing videos in the squares," he added. "Daily, things are improving."

The available opinion polls show Mursi way behind others including ex-Arab League chief Amr Moussa and Abdel Moneim Abol Fotouh, an independent Islamist who parted ways with the Brotherhood last year to pursue his own presidential bid.

The polls reflect the challenge facing the Brotherhood as it seeks to turn its success in legislative elections earlier this year - it won nearly half the seats in parliament - into executive power in the May 23-24 nationwide presidential vote.