| Protesters defaced a poster of Saleh at a rally outside Sana'a University last week [Reuters]
Anti-government protests in Yemen could come to a head in the coming days, as president Ali Abdullah Saleh competes for tribal support with the scion of one of the country's most powerful families.
Saleh has long been adept at manipulating Yemen's complex tribal dynamics to preserve his decades-old grip on power. He is the head of a vast nationwide patronage network, handing out money and other rewards to loyal tribal chiefs, who then redistribute some of those resources to members of their tribes.
Just last week, Saleh reportedly distributed new cars and more than 20 million Yemeni rials ($93,000) during a meeting with tribal chiefs.
But his support is beginning to erode: Hussein al-Ahmar, a chief in the Hashid tribal confederation - Yemen's most powerful (though only its second-largest) - announced on Saturday that he was resigning from the ruling party, the General People's Congress. Al-Ahmar announced his resignation at a rally in the northern Amran province, which was attended both by members of the Hashid and the Baqil, Yemen's largest tribal confederation.
A second high-profile resignation last week came from Mohammad Abdel Illah al-Qadi, a leader of the Sanhan tribe, which is a member of the Hashid. His desertion is at least symbolically significant: Saleh himself comes from the Sanhan.
Yemen's tribes are hardly monolithic, though, and other members of the Hashid and Baqil quickly announced their support for the government.
"A number of sheikhs in Baqil have put out a statement, claiming that Hussein al-Ahmar does not speak for them, and indeed he does not - it isn't even clear if he speaks for Hashid," said Gregory Johnsen, an expert on Yemen at Princeton University, in an analysis of al-Ahmar's resignation.
Nor is al-Ahmar's defection entirely surprising. He is the son of the late Abdullah al-Ahmar, the former leader of the Hashid and a longtime ally of the president's. But the family's loyalties have splintered since Abdullah's death in 2007. It continues to wield considerable political influence: One of Hussein's brothers, Himyar, is the deputy speaker of parliament; another, Hamid, is a prominent businessman who is considered a potential successor to Saleh.
Hamid has opposed Saleh for a number of years - in a 2009 interview with Al Jazeera, he accused the president of treason. Hussein's decision to quit the GPC, then, simply places family ties above political loyalties.
Still, there are also reports of tribesmen joining the anti-government protesters in Sanaa, the capital, some of them with economic grievances. Yemen's oil reserves are fast being depleted - the country is expected to run out of oil by 2017 - and diminishing revenues mean Saleh can no longer afford to buy off all of the country's tribal leaders.
Saleh has attempted to rally other tribal leaders to his side: The Wall Street Journal reported on Sunday that 11 tribal sheikhs pledged their support to Saleh.
"There is a negative impact to this tribal mobilisation. It polarises the country," Abdul Ghani al-Iryani, a prominent Yemeni political analyst, told Al Jazeera. "It subtracts from the power of what was a popular political protest... it makes it more militaristic and regional."
The volatile south
The slow erosion of Saleh's northern tribal support would be significant, because that support is a main pillar of his presidency.
He has long been unpopular in southern Yemen, where many complain of being treated as second-class citizens by the northern-dominated government.
Unemployment, poverty and poor public services have turned the south into the epicentre of the anti-government protests that began two weeks ago. In Aden, the main city in the south, 40 per cent of young people are unemployed - and that's the official statistic.
One Yemeni newspaper reported that a million people took to the streets during a rally last week in the city of Taiz. That would be an impressive feat - the entire population of Taiz is perhaps half a million - but the exaggerated numbers still suggest a massive turnout.
Notably, though, protesters in the south have dropped their usual call for secession, rallying instead for Saleh's ouster - aligning their demands with those of their counterparts in the north.
"I've always argued that the call for secession came out of desperation," al-Iryani said. "It's possible that the majority of southerners still have a realistic view about secession."
Saleh last week ordered his security forces to protect demonstrators, but those in the south (and in the north, though to a lesser extent) continue to face violence from police and plainclothes security men. Four people were killed by police on Saturday during a rally in Aden, and dozens wounded, according to local officials. At least 19 people have been killed in Aden alone during the last two weeks.
The Houthis in northern Yemen - a group that has fought a bloody on-again, off-again civil war with Sanaa since 2004 - also announced their support for the anti-government protests.
Desertions from the ruling party could continue, too: 59 members of the GPC have threatened to resign over violence against protesters.
Saleh has tried to downplay the protests: In a speech to members of the armed forces, he described them as an outside conspiracy to divide Yemen, according to the state-run SABA news service.
But the protest movement actually appears to be uniting Yemen's normally fractious opposition - though the increasing tribal role in the protests could reverse that trend.