Washington's Mideast peace efforts are in trouble as it is, but an additional complication is often overlooked: Should 76-year-old Palestinian President Mahmoud Abbas, a heavy smoker prone to threats of resignation, leave office, there's no designated successor and no agreement on how to choose one.

Having a Palestinian leader opposed to violence is key to U.S. policy in the region, and Abbas has filled that role for the past six years. A turbulent transition could seriously weaken any new leader.

The issue of succession is so sensitive it's rarely discussed openly by the Palestinian elite, and Abbas is touchy about it.

When a U.S. newspaper wrote about the leadership ambitions of key players in his Fatah movement, the official Palestinian news agency ran a scathing statement directed at one of those mentioned in the article, former Palestinian envoy to the U.N., Nasser al-Qidwa.

Abbas also went after another Fatah prince, Mohammed Dahlan, stripping him of privileges and shutting down his TV station earlier this month, after Dahlan criticized the president in meetings with activists.

Abbas aides play down concerns about his health, prompted by his smoking and recent weight gain. They say he's fine and that getting dental implants was his only recent medical procedure. Occasional threats to step down are simply attempts to create leverage vis-a-vis Israel and the U.S., they say.

At the root of the succession problem is the split of the Palestinian territories between Fatah, which now controls the West Bank, and the Islamic militant Hamas movement, which wrested control of the Gaza Strip from Abbas in 2007.

Fatah and Hamas have been unable to reconcile, and their rivalry has prevented presidential and legislative elections, which should have taken place by this year.

Abbas was elected to a four-year term in 2005. The Hamas-dominated parliament stopped functioning long ago, in part because Israel arrested many Hamas legislators.

Palestinian law calls for the speaker to serve in a 60-day caretaker capacity until elections to replace a president. This arrangement was used in the transition from Yasser Arafat, who died in November 2004, to Abbas two months later. However, the current parliament speaker is from Hamas, and it's unlikely Fatah would agree to let Hamas take over the presidency, even temporarily.

Elections also are seen as improbable since they are tied to elusive reconciliation. In this case, Fatah would have to appoint a successor, though the nominee would be vulnerable to claims by Hamas and others that he has no legitimacy.

Fatah, which has long dominated Palestinian affairs, has been in disarray since it lost parliament elections to Hamas in 2006, with voters punishing the former ruling party for arrogance and mismanagement. Fatah's troubles have been compounded by its failure to establish an independent Palestinian state. If elections were held, it's not certain Fatah would defeat Hamas.

The most popular Fatah leader of the middle generation is Marwan Barghouti, who is in his late 40s, but he is serving a life sentence in Israel for his role in the armed Palestinian uprising earlier this decade.

Among the remaining contenders, rivalry is so intense they might be unable to agree on a consensus candidate or settle on a weak one.

"Fatah suffers a leadership crisis," said Palestinian analyst Khalil Shekaki. "So far it hasn't presented a No. 2 leader."

Abbas wanted a vice president and early in his term called for creating such a position, said an aide, Nabil Shaath. However, once the parliament stopped functioning, it was no longer possible to make the necessary changes in the law, Shaath said.

Abbas hasn't openly designated a favorite in Fatah, though he has given a push to chief negotiator Saeb Erekat, perhaps his most loyal aide. Abbas lobbied for Erekat in Fatah elections in 2009 and gave him a coveted seat in the PLO Executive Committee, a key decision-making body.

Another name being floated by political insiders is al-Qidwa, whose international experience at the U.N. and family ties to Arafat — he is the iconic leader's nephew — are seen as a plus.

Al-Qidwa was the one named in the Abbas-authorized response to the newspaper report on the succession battle. The commentary, published by the official news agency Wafa, complained that local politicians were engaged in rumor-mongering. Al-Qidwa denied involvement and has since patched things up with the Palestinian leader.