The large number of Egyptian voters undecided between candidates touting radically different futures for the country, and the novelty of a free presidential vote make this week's election almost impossible to call, pollsters say.
The candidates, from Islamists to former members of ousted Hosni Mubarak's regime, have seen their fortunes swing wildly in almost weekly polls conducted by a government funded think tank and an independent survey centre.
But even support for the leading candidate in a May 16 poll, former premier Ahmed Shafiq, is dwarfed by the large number of undecided voters who may tip the election's result in another candidate's favour, said a prominent pollster.
"The candidate with the most support was still below the undecided," said Maged Osman, who heads Baseera, an independent survey centre.
Most polls conducted by Baseera, the government funded Al-Ahram Centre for Political and Strategic Studies and the government's research arm show four front runners.
Two of them are likely to go into June run offs after the May 23 and 24 vote, the first presidential election since an uprising toppled Mubarak in February 2011.
Former foreign minister and Arab League chief Amr Mussa has consistently ranked first in weekly surveys conducted in countrywide face to face interviews by the government funded think tank Al-Ahram Centre for Political and Strategic Studies.
But he dipped nine points, to 31 percent, in a May 20 poll, followed closely by Ahmed Shafiq, a tough talking former air force general who was Mubarak's last premier.
The powerful Muslim Brotherhood's candidate Mohammed Mursi came third, his best showing yet, with independent Islamist Abdel Moneim Abul Fotouh in fourth place.
In Baseera's last poll on May 16, conducted with a sample of 2,200 people from across Egypt over mobile phones and land lines, Shafiq led with 19.3 percent, followed by Mussa with 14.6 percent and Abul Fotouh with 12.4 percent.
But 33 percent of those surveyed said they were undecided.
A poll by the government's Information and Decision Support Centre on May 19 also showed Shafiq leading with 12 percent, with Mussa in second place with 11 percent.
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The fluctuating polls and contradictions between the surveys have prompted accusations, particularly from some candidates, of pollster bias and incompetence. Mursi's campaign compared them with "astrologers".
But pollsters say the changes in the results reflect the novelty of a free election in the historically authoritarian country and its fragmented politics after the uprising.
"Within each trend, there is intense competition between the candidates. The political trends could not decide on a candidate," said the Ahram centre's head of polling, Ahmed Nagui Kamha.
"This is the first time Egyptians elect a president. You used to choose between Mubarak and Mubarak," said Osman, who once headed the government's survey centre under Mubarak and then served as a minister after the dictator's ouster.
"Before, there wasn't much distinction between rhetoric. Now its very different," he said of the candidates' platforms.
Other factors have also played into the candidates' rankings, Osman said.
He said that Shafiq, who was forced to resign a month after Mubarak's ouster by massive street rallies, won sympathy, particularly among female voters, after his wife died last month.
Shafiq, who campaigns on a severe law-and-order platform the appeals to voters disillusioned with a spike in violence over the past 15 months, also benefited from a deadly protest outside the defence ministry on May 4, he added.
But the final say will belong to the undecided and perhaps the candidate who is most efficient at bringing out the vote, pollsters said.
"They will change the results completely," said Sahar Ammar, head of polling at the government's Information and Decision Support Centre.
That may yet help Mursi, who although behind other candidates, enjoys the support of the Muslim Brotherhood's countrywide network of activists that helped the Islamists win parliament and senate this year.
"There is the element of the last minute decision, and that can be affected by the Muslim Brotherhood's machinery for mustering voters," said Osman.