© UnknownFawaz Gerges of the London School of Economics and Political Science.
If President Mubarak's support was representative of the population, you would have expected tens of thousands to come out in full force over the last week. But the ruling party hasn't been able to mobilize people. It isn't a lack of resources: it's simply that there are very few who would go out on a limb to defend them.

The regime's base is extremely shallow in comparison to the opposition, which represents an overwhelming majority of the population. The regime has alienated most of the rising social and political classes: centrists and democrats, leftists, nationalists, independent Islamists, and the Muslim Brotherhood. They're left with about 10 per cent of the country, the uppermost echelon of the population.

It's a strategic alliance between the business class and the ruling elite, with the support of the state security apparatus, which numbers about a million people. Mubarak's allies hold the top cabinet positions, and his new Vice-President is a very close supporter. But outside that structure there is really no support at all.

There is one other ingredient in his support base that is less secure, and will probably prove the deciding factor: the military. There is no doubt that there are those in the top brass who believe in his politics, who believe in the status quo and stability. And as an institution, the army is calling the shots.

It, too, has people in the very highest echelons of the government; and Mubarak has a strong connection to the military thanks to his former position as chief of the air force, and over the past two decades he has co-opted scores of the senior officers who have a vast interest in the continuation of the regime. He has appealed to that loyalty in recent days, and the army still wants to find a face-saving formula. That is why they will not do as the Tunisian army did and abruptly force him out. This is an institution with a powerful memory.

Nonetheless, the situation is very far from secure for Mubarak. The army knows that the writing is on the wall: they are trying to assert control and find a formula for an honorable exit. But the moment they realize that the disadvantages of the status quo outweigh the advantages, they will say: you must give up power now.

The army finds itself under tremendous pressure, between the rock of its institutional instincts and interests and the hard place of public and international opinion, in particular now that even the Americans have come to the conclusion that Mubarak is a liability.

In the senior ranks, they are asking: how much damage have we incurred? Should we play for time, or assert control? Equally, they know that junior officers and conscripts are not on the same page, being much closer in outlook - ideologically, socially, economically - to the people on the streets. The top brass are well aware that even if they decided to go all the way in support of Mubarak, they might not be able to get their juniors to follow orders.

That is the position as we reach today, the moment of truth. If huge crowds come out and try to march to the presidential palace, the army will be forced to make its decision. The balance of power seems to be in favor of the opposition. Today we will find out how far the army is willing to go to redress that.

The author is director of the LSE's Middle East Centre