Ali Abdullah Saleh, Yemen's president, has tried to defuse ongoing anti-government protests by offering to form a unity government. The offer was quickly spurned by the Joint Meeting Parties (JMP), a coalition of opposition parties, which called it a "waste of time".
Their quick rejection meant Saleh did not have to answer an important question: who, exactly, would be included in this unity government?
Yemen's opposition, indeed its entire political system, is deeply fractured. There are organised opposition parties within the JMP, which brings together, among others, socialists and Islamists. There are tribal elements, like the Ahmar family, fast emerging as Saleh's main challenger. And there are insurrections in the north and south, both of which have longstanding grievances with Sanaa.
Saleh likes to portray himself as the only man capable of keeping Yemen united. There is a strong element of fearmongering in that boast, of course, but also a grain of truth: It's unclear what role Yemen's various political and tribal factions would play if Saleh quits.
Islah (Reform) Party
The Islah is the main opposition party in Yemen, and currently holds about 20 per cent of the seats in Yemen's legislature. Islah had played an on-again, off-again role in the Yemeni government. It joined the government in 1994, at the end of Yemen's civil war, only to withdraw in 1997 following a poor showing in legislative elections.
The party pulls together both Islamists and tribal elements. Yemen's Muslim Brotherhood is part of it, as is Abdul Majid al-Zindani, a Salafi preacher who is considered a "specially designated global terrorist" by the United States. The party also incorporates members of the Ahmar family (see below). It was founded by Abdullah al-Ahmar, the family's late patriarch.
The party suffers from deep internal divisions over its relationship with the government, the role of women in politics, and other issues. The Salafi wing of the party, for example, is deeply sceptical about engaging with the ruling party. Thus Islah has been minimally effective as a political player, with few (if any) legislative accomplishments to its name.
Joint Meeting Parties
The Islah party has since become a part of the JMP, a coalition formed in 2002. It also includes the Yemeni Socialist Party (YSP) - still somewhat popular in the south, where it was once the ruling party - and three other minor parties (Al-Haq, the Unionist party, and the Popular Forces Union party).
Given its eclectic makeup, the JMP is - not surprisingly - also plagued by divisions. These occur both between parties and within individual parties - Islah's Islamist/tribal splits, for example, or the YSP's uncertainty about how to interact with the secessionist Southern Movement (see below).
Thus the JMP has struggled to articulate a political platform. It has called for a few obvious reforms - less corruption, a more democratic government - all of which are universally popular. But it has struggled to win widespread support and articulate a clear legislative platform.
One of Saleh's main political challenges comes from the sons of the late Abdullah al-Ahmar, the former leader of the Hashid tribal confederation. Abdullah was a longtime ally of the president's, but his sons are less loyal - particularly Hamid, a prominent businessman who is considered a potential successor to Saleh.
Hamid has opposed the president for a number of years - in a 2009 interview with Al Jazeera, he accused the president of treason.
Several other Ahmar brothers help to make the family a potent political force. Himyar al-Ahmar is the deputy speaker of parliament, and Hussein al-Ahmar is a leader of the Hashid - though his influence is limited - who resigned last week from the ruling General People's Congress.
"The Ahmars are the paramount sheikhs of the Hashid confederacy," said Abdul Ghani al-Iryani, a prominent Yemeni political analyst. "They clearly think this is an opportunity to take what they're entitled to."
It is hard to imagine the Houthis, who have fought an on-again, off-again civil war with Sanaa since 2004, playing any role in any "unity government" sponsored by Saleh.
Their grievances are complicated. They worry that their religion (the Houthis are Zaydi Shia) is threatened by creeping Wahhabi influence; and they are frustrated with the economic marginalisation of the north, particularly Saada province. Sanaa, in turn, has accused the Houthis of being Iranian agents.
Various cease-fires since 2004 have inevitably collapsed, and so the Houthis' political role has been extremely limited. Saleh said last year, following the most recent truce, that the Houthis could form a political party and contest elections. But they have had little involvement with Yemeni politics since.
The Houthis issued a statement endorsing the anti-Saleh protests, but it is unclear what role, if any, they would seek to play in a post-Saleh Yemen.
Also murky are the desires of the secessionist Southern Movement. The movement's leaders have temporarily dropped their demands for independence, choosing instead to support the protests and call for Saleh's ouster. If he is to fall, it is uncertain though whether the Southern Movement would revert back to demanding secession.
The movement traces its roots back to 1994, when south Yemen tried (and failed) to secede from the north. Its longstanding grievances are economic: Sanaa has not done enough to develop the south's economy, the movement argues, and many northerners enriched themselves by illegally seizing land from southerners.
Its anti-government demonstrations have increased over the last two years, and the movement enjoys popular support from many in the south. And its grievances are systemic: Saleh's resignation would not, by itself, resolve Yemen's economic inequality.