Hardline Islamists back Aboul Fotouh for Egypt president
Egypt's ultra-conservative Islamist groups have chosen to back Abdul Moneim Aboul Fotouh in the presidential race, rather than the candidate of the powerful Muslim Brotherhood.
The former jihadist group, Gamaat Islamiya, has announced its support after the main Salafi party, Nur made its decision at the weekend.
Experts say it is a serious blow for the Muslim Brotherhood.
The development comes as official campaigning for the presidency begins.
Doctor Aboul Fotouh was expelled from the Brotherhood last year after he announced he would join the contest. At that stage, the mainstream Islamist movement said it did not plan to field a presidential candidate but it later reversed the policy.
It has nominated the head of its political party, Mohammed Mursi.
'Crisis for Brotherhood'
The backing for Dr Aboul Fotouh should bring him many of the votes that took the Salafists, who are highly conservative and draw inspiration from the life of the Prophet Muhammad and the earliest Muslims, into second place behind the Brotherhood in last year's parliamentary elections.
The small, moderate Islamist party, al-Wasat, has also switched its support to him.
"This totally alters the political calculus in Egypt today. I think Mursi's chances of winning have dropped significantly," says Shadi Hamid of the Doha Brookings Centre.
"This is a major split in Islamist ranks and a crisis for the Muslim Brotherhood. They face the prospect of defeat by one of their own dissidents."
Members of the other Islamist movements say they are backing Dr Aboul Fotouh, who is seen as more liberal than Mr Mursi, because they feel he is a stronger candidate but also to stop the Brotherhood dominating both parliament and the executive branch.
The developments leave the Brotherhood looking weaker as it moves closer to a confrontation with Egypt's ruling generals.
It has called for the government to resign or be sacked by the Supreme Council of the Armed Forces.
Parliamentary sessions have been suspended for a week in protest at its performance.
Islamists v secularists
Overall, the presidential contest looks set to be dominated by Islamists and secularists who served under the ousted president Hosni Mubarak.
Besides Dr Aboul Fotouh and Mr Mursi, the former Egyptian foreign minister and head of the Arab League, Amr Moussa, is considered a front-runner.
There are a total of 13 candidates in the race.
From Monday all can officially display their posters in public and broadcast messages on television until two days before polls open for the first round of voting on 23 and 24 May.
However many have already held unofficial rallies and political banners were put up across the country weeks ago.
There have been many surprises in the run-up to start of campaigning.
Three leading candidates were disqualified from the final list by the election commission.
They included Khairat al-Shater, a deputy leader of the Muslim Brotherhood, who was its original chosen nominee, and the popular Salafist preacher and lawyer, Hazem Abu Ismail.
Supporters of Mr Abu Ismail have been staging a protest outside the Defence Ministry in Cairo. One was killed in clashes on Saturday.
Ahmed Shafiq, the prime minister appointed by president Mubarak just days before he was ousted from power, was allowed to stand for the presidency after the commission went back on an earlier decision to exclude him.
If the first round of polling does not produce a winner with more than half the votes, a second round will take place on 16 and 17 June.
Egypt's military has promised that the vote will be free and fair and says it will hand over power by the end of June.