The confrontation in Egypt could very well mean not only the end of a flawed democratic transition, but a more fundamental change in the basic civility of Egypt’s politics.
Battles for legitimacy in Egypt will not end with tomorrow's protests
There is a cottage industry based around predicting what will happen tomorrow, when tens of thousands - perhaps hundreds of thousands - of Egyptians are expected to take to the streets to demand the departure of the president, Mohammed Morsi, on the anniversary of his first year in power.
Scenarios are outlined. Possible paths for this latest somersault in the country's turbulent trajectory are calculated. Bets are made on who stands to benefit and who might lose. In truth, it is very hard to predict what will happen. But the coming confrontation could very well mean not only the end of a very flawed democratic transition, but a more fundamental change in the basic civility of Egypt's politics.
Backers of the Tamarrod (Rebellion) movement, which now includes almost all of the secular opposition and even some Islamists, are basking in a sense of determination and confidence rarely seen since Hosni Mubarak was overthrown in February 2011.
Mr Morsi, his Muslim Brotherhood and their allies are firing back with their own bluster, a campaign they have called Tagarrod (Impartiality). They are shaken by the challenge they face but resolute that they are defending democracy.
Both sides now claim to have the support of at least 20 million Egyptians, although their signature-collection drives are unverifiable. Traditional and social media on each side of the divide are amplifying these sentiments, driving a battered Egyptian people into a sense of angst-ridden frenzy. Amid chronic fuel shortages - the result of government mismanagement, say the rebels, or of manipulation and irrational hoarding behaviour, say the loyalists - the reigning atmosphere is one of fevered hysteria.
In imaginations more than in reality, a country is falling apart. The danger is that the conflict that thus far exists mostly in rhetoric could become real.
As the recent lynching of Shias near Cairo shows, a new tolerance for grisly violence is emerging in Egyptian society. The posturing and vivid language of political discourse, replete with visions of streets awash in blood, is almost certain to translate into more deaths in the weeks ahead.
The Egyptian uprising and its aftermath have already claimed more than 1,000 lives, but - particularly since both police and army are advertising that they will limit their role in Sunday's protests to protecting essential facilities - the difference now is that it will not be citizen against state. It will be citizen against citizen.
There are three types of legitimacy battles playing out today in Egypt. One is revolutionary - every political player claims to act in the name of the revolution, and legitimates actions in the name of the revolution. The Tamarrod campaign seeks to redress what it sees as the revolution's hijacking, while the Tagarrod campaign claims to protect the revolution from an undemocratic threat.
When the Muslim Brotherhood and its allies rushed the adoption of a new constitution last December, or battle the judicial establishment as they have in recent months, it is in the name of revolution.
Never mind that more than two years after the revolutionary act of deposing a dictator, many compromises with the old establishment, and the creation of a new constitutional order, the time for revolutionary acts has passed.
Likewise, the Brotherhood's opponents have never accepted that a new order exists - they see it as a perversion of the revolution, one they wish to correct, if necessary through a new uprising.
The second legitimacy is electoral. The Muslim Brotherhood has gained a plurality of votes in parliamentary elections and its candidate won the presidential election. This is the basis of its right to govern, and why it sees the movement to depose Mr Morsi - indeed to reset the entire post-Mubarak transition - as undemocratic and reactionary.
The dissolution of the lower house of parliament by the Supreme Constitutional Court and the military last June was, from their perspective, a first salvo to roll back their progress from banned movement to dominant political force.
Efforts to stall or undo the transition agenda that they had engineered with the military were a second, and the Tamarrod campaign is a final attempt to undo the result of elections that, at the time, were widely accepted as free and fair.
Mr Morsi was formerly a key electoral strategist of the Muslim Brotherhood, and he and his group are very good at electoral politics. But he has not been as good at everyday politics, at creating a sense of confidence and trust beyond his natural constituency. And his moves to counter the above threats, most notably the authoritarian decrees he issued in late Novemberlast year (with dubious authority) have undermined his own standing. As Nawara Negm, a writer and activist, has argued, Mr Morsi does not know how to cajole his people.
The final source of legitimacy is institutional - the traditions, practices and power centres of the Egyptian state. These have been threatened by the revolutionary trend, which seeks to transform them, and by the rise of a political movement widely seen as intent on taking over institutions. The military, the civilian security services and the judiciary have thus far shown the most resistance and ability to alter the course of the post-Mubarak transition.
But even beyond these, the Morsi administration finds itself facing tremendous institutional inertia, with each part of the bloated machine of the Egyptian state seeking to secure its autonomy and privileges. This mastodon was never going to be tamed by a single political force, and the country's divisions have meant that, in practice, each side of the political divide seeks to co-opt rather than reform. This is why the army, in particular, appears to be waiting to see what happens before choosing sides.
The logjam among these three legitimacies has led to the present moment. Without a genuine willingness to engage in dialogue and a stand-down from the maximalist positions taken up by both sides, it will not end well for civilian political actors no matter who, if anyone, emerges "victorious".
If Mr Morsi is successfully toppled, the unlikely coalition of revolutionaries and reactionaries that has united against him will fall apart the day after. The Tamarrod movement, in attempting to re-create the energy of the anti-Mubarak protests of 2011, is repeating the same basic mistake: it is entirely negatively framed, and has no positive demands. And it will face a wounded, seething Islamist movement that will seek to undermine whatever order emerges next, violently if necessary.
And if Mr Morsi wins the day through repression and without drawing the lessons of the antagonism he has created, he will only find the country even more difficult to govern.
Issandr El Amrani is an independent journalist based in Cairo who blogs at arabist.net
On Twitter: @arabist