Sheik Sadeq al-Ahmar has taken on the mantle of leader of the movement to oust Saleh, his onetime ally, after 32 years in power. Al-Ahmar's abandoning of Saleh two months ago was a heavy blow, but he's become even more of a threat now, with his tribal fighters battling Saleh's security forces in the streets of the capital.
"Al-Ahmar turned into a leader whom everyone else is rallying around," said Yemeni political analyst Faris Sadqaf.
More than 120 tribal fighters and troops have been killed in this week's violence, raising fears the country could be thrown into civil war. The fighting spread beyond the capital on Friday as tribesmen allied to al-Ahmar seized a Republican Guard military camp in the Fardha Nehem region about 50 miles (80 kilometers) to the northeast.
It's a lesson in the clan intrigue that underpins Yemen's politics, commerce and society.
Few adversaries in Yemen have more resources than the 55-year-old al-Ahmar: a mix of warlord, tycoon and kingmaker.
He commands thousands of fighters from the Hashid tribal confederation with arsenals that include rocket-propelled grenades and mortars _ and can likely summon more. Many of his nine brothers have played prominent roles in Yemeni politics and commerce. One owns a phone company, a bank, a TV network and franchises for the fast-food chain KFC and the Western-style Spinneys supermarkets.
The family investments stretch into the United Arab Emirates and Saudi Arabia, which pays the Hashid monthly for their loyalty in defending the Saudi-Yemeni border.
Unconfirmed reports in Yemen claim al-Ahmar's take used to top $5 million a month.
But the essence of al-Ahmar's power is as a political godfather. At one time, it helped prop up Saleh's nearly 33-year rule.
Al-Ahmar took over as the head of the Hashid after his father, Abdullah, died in 2007. In effect, it's like running a state within a state. The Hashid confederation has hundreds of thousands of people under its umbrella of nine tribes _ including Saleh's own, the Sanhan. Many of the Sanhan's members have turned against the president since the uprising began in February.
Al-Ahmar also inherited an alliance with Saleh. His father was parliament speaker for 10 years and led the Islah Islamic party, an opposition bloc dominated by tribal sheiks and Islamists that did not directly threaten Saleh's regime.
Saudi Arabia appeared to be the glue that kept the Hashid with Saleh.
According to Abdullah al-Ahmar's autobiography, the Hashid refused to back Saleh after he rose to power following the assassination of President Ahmed al-Ghamshi in 1978. The Hashid ruler opposed Saleh's deep military background, which began with his joining the army as a teenager.
"Yemen doesn't need a military man but a civilian man," the late al-Ahmar wrote.
Saleh, however, appealed directly to neighboring Saudi Arabia, which traditionally has signed off on Yemen's leadership. It worked, and Saudi officials persuaded the Hashid to back Saleh.
This proved a critical foundation for Saleh as Yemen struggled through a unification of the pro-Saudi north and communist south in 1990. The Hashid tribal fighters currently battling Saleh fought on his side in a 1994 war to crush a separatist movement in the south.
The U.S., meanwhile, considered Saleh's tribal ties an essential tool in the fight against an al-Qaida offshoot in Yemen _ now seen as the world's most active. The group, known as al-Qaida in the Arabian Peninsula, is linked to the attempted Christmas Day 2009 bombing of an airline over Detroit and explosives found in parcels intercepted last year in Dubai and Britain.
Al-Ahmar publicly supported Saleh in his fight against al-Qaida and condemned the terror group. But he was also sharply critical of the president, saying he was not really serious about fighting the group and was only milking the counter-terrorism campaign to extract millions of dollars worth of aid from the Americans. Hashid tribes have little presence in the Marib and Abyan provinces where the estimated several hundred members of al-Qaida's branch are believed to be hiding out.
The bonds between Saleh and al-Ahmar broke one by one.
First, al-Ahmar tried to mediate between the government and protesters after the mass street protests calling for Saleh's ouster began. He then turned his back on Saleh after security forces on March 18 opened fire on unarmed marchers in Sanaa, killing dozens. The bloody day prompted an avalanche of defections among Saleh allies.
"We joined the street when we said, `We can take anything, but not the bloodshed.' We told him no bloodshed," al-Ahmar told The Associated Press on Thursday.
Still, al-Ahmar didn't send his fighters into confrontations with security forces, as the opposition insisted it wanted to keep its campaign peaceful.
That changed earlier this week after Saleh's forces tried to storm al-Ahmar's compound.
"Saleh is a member of our tribe, but he turned bloody," al-Ahmar said. "Saleh wanted to create discord in the country and he wanted to drag us to a civil war." Gregory Johnsen, a Yemen expert at Stanford University, said the street battles surprise few who follow the country's rivalries.
"It has been clear for some time that Saleh's family and the al-Ahmar family were headed for some sort of showdown," he said.
But even what appears to be a two-sided fight is more complex in Yemen. Saleh still has many side pacts and alliances across Yemeni society, including an arranged marriage between one of Saleh's daughters and a prominent Hashid member, said Johnsen.
"You have all these overlapping webs of allegiance now," he said. "So getting the president out is going to be difficult." The cohesion of Saleh's military _ heavily staffed with friends and relatives _ could be a tipping point. A serious crack occurred in March with the defection of 1st Armored Division commander, Maj. Gen. Ali Mohsen al-Ahmar, who is not related to the other al-Ahmars. So far, the general's 50,000 troops and other heavily armed opposition groups have not entered the fighting between the Hashid and Saleh's forces.
Longer term, Johnsen said it remains unclear if Sadeq al-Ahmar or any of his brothers will seek to replace Saleh.
Their main goal, he said, is oust him and his followers.
"For the al-Ahmar family to remove Saleh from the equation right now is a win for the al-Ahmar family. They wouldn't need the presidency to consider it a win," said Johnsen. "Consider it a zero-sum game. Removing their biggest rival, even if they don't take his place, still gives them more power."