The militant al-Aqsa Martyrs’ Brigades has announced it will back his candidacy to replace Yasser Arafat in the January 9 election.
Mr Abbas is known as a moderate and there were questions over whether he might be opposed by the al-Aqsa Martyrs’ Brigades, the armed wing of the Fatah movement.
Abbas’s most formidable rival, Marwan Barghouti, is said to have influenced the militants.
Currently serving a life sentence in an Israeli prison, Barghouti announced his decision on Friday not to run in the presidential elections.
Barghouti then urged his supporters to back Mr Abbas.
The divided factions of the al-Aqsa Martyrs’ Brigades came together to issue the joint statement in support of Mr Abbas candidacy.
In the past, Mr Abbas has been a vocal critic of the armed Palestinian uprising, and some militant factions fear he will not be tough enough in negotiations with Israel.
Mr Abbas, also known as Abu Mazen, was nominated as Fatah’s only candidate for January’s elections at a Fatah Revolutionary Council meeting in the West Bank city of Ramallah on Thursday.
Abbas is now the clear favourite to succeed Mr Arafat as President, having already replaced him as chairman of the Palestine Liberation Organisation (PLO).
The governmental State Information Service poll showed Abbas receiving 41% of the vote, followed by human rights activist Mustafa Barghouti with 20%.
In other developments, Israeli Prime Minister Ariel Sharon has told US magazine Newsweek he is ready to meet with Chairman Abbas.
Mr Abbas responded by saying he would be willing to meet Mr Sharon.
In the interview, Mr Sharon said he would seek to co-ordinate the withdrawal of Jewish settlers from the Gaza Strip.
Abbas responded to Sharon’s comments on the Gaza withdrawal saying Israel needed to allow the Palestinians to build the security infrastructure in Gaza before the settlers’ withdrawal.
Mr Sharon added that he was going to make every effort to co-ordinate the disengagement plan with the new Palestinian government.
He also said that Israel would keep its troops away from Palestinian towns during the January poll “to enable them to conduct their elections with as little interference as possible”.