The first real collision between Mohammed Morsi's Islamic Brotherhood, catapulted into power in Egypt's first free elections since the toppling of the dictatorial Hosni Mubarak in 2011, and the ruling Supreme Council of the Armed Forces is likely to come over formulating a new democratic constitution.
Morsi, the first Islamist to become the leader of an Arab state, is on a collision course with SCAF, a council of 21 generals appointed by Mubarak.
It has governed Egypt since Mubarak was driven from power and has sought to undermine Morsi from the moment he was elected June 24 after defeating the generals' candidate, former air force chief Ahmed Shafiq.
SCAF, seeing its power challenged, moved swiftly to clip Morsi's wings just before he was inaugurated by taking over presidential powers and the legislative authority of the Islamist-dominated Parliament.
That suggested the council did not plan to keep its pledge to step down once a new president was in place -- that is to say, Shafiq.
Morsi hit back by revoking SCAF's decision to dissolve Parliament, the first freely elected national assembly in Egypt's history, that put the generals a position to dictate the new constitution.
Some saw that as a constitutional coup by Morsi that showed no regard for democracy, or for the judiciary the generals are using as a front.
Parliament duly convened Tuesday, but it was little more than a symbolic act of defiance. After a 5-minute session it adjourned, leaving both sides to return to their respective corners.
"A threatened collision was instead turned into rituals of institutional respect," the Financial Times observed.
The Brotherhood, which spent decades in the political wilderness before stepping out of the shadows when Mubarak fell, "are not by nature precipitate," the FT noted. "Their tactics are those of the long march.
"The real clash will come over the new constitution. Mr. Morsi has conceded that elections for a new parliament should take place after the constitution is agreed."
The generals do not want to see the Islamists, their longtime enemy, in power and have left no doubt they will fight tooth and nail to prevent Shariah religious law being imposed.
Many of Egypt's 82 million people don't want to see that either, so the generals, for whom Egyptians have little love, will find considerable public support on that score.
But Egyptians don't want military rule either, and the mobs could return to the streets if the generals seek to perpetuate their power.
"Islam should, of course, be recognized as one fount of law, but never overriding universal rights," the Financial Times commented.
"This debate is central not just to Egypt's future. Getting it right will shape the future of the region."
Morsi, an American-trained engineer and former lawmaker, stands at the crossroads of history. He's Egypt's fifth president and the first from outside the military establishment.
The generals have been dismissive of Morsi. SCAF advisers speak of him as "a transitional president who will not stay long, whether he likes it or not."
So far the generals haven't mobilized their forces on the streets to challenge the Islamist victory, a move that would almost certainly trigger the kind of bloodshed that finally forced an end to Mubarak's 30 years of brutal, corrupt rule.
Neither has Morsi called out the Brotherhood's masses and their allies onto the streets in a direct challenge to the military, which is prepared to protect its privileges and its economic power if these are threatened.
But the new president, and the Brotherhood, will inevitably have to confront the generals or forever lose their authority as the people's choice.
The Americans appear to be prepared to accept the realities of the tumultuous events in Egypt over the last 18 months and to give Morsi, and the Islamists, some space to prove themselves.
U.S. Secretary of State Hillary Clinton will visit Cairo shortly, and Morsi has been invited to visit Washington.
Washington has already urged the generals to speed the transition to democracy. But they know if they give in now, their era will be over.
For now both sides are waging what's largely a legalistic contest. But a showdown is looming.