The protests rocking Egypt could change the political landscape of the all the Arab countries and beyond. Possible outcomes range from pro-democracy forces taking charge in Cairo to, in a worst case, an all-out war that brought in Israel and Iran.
In between, there could be a long period of instability that could breed economic chaos across the region and derail economic recoveries in the United States and Europe.
In Cairo, embattled President Hosni Mubarak declared to his nation in a televised address Tuesday night that he would not stand for re-election but would not leave office either, determined to stay in power until elections in September. Mubarak did not to rule out his son as a candidate.
Later, President Barack Obama talked by phone to Mubarak for 30 minutes and said in brief remarks at the White House that the Egyptian leader "recognizes that the status quo is not sustainable and that a change must take place."
But, Obama emphasized, he indicated directly to Mubarak that it "is my belief that an orderly transition must be meaningful, it must be peaceful and it must begin now." That appeared to imply that the president was not particularly enthusiastic about Mubarak's decision to wait until September.
Mubarak made his halfway concession as hundreds of thousands of Egyptians gathered in a major square in Cairo to demand an end to his 30-year rule.
The doomsday scenario for the U.S.
Egypt, the world's largest Arab nation, is critically important to U.S. foreign policy and to major goals the Obama administration is pursuing in the Middle East: the Israeli-Palestinian peace process, containment of Iran's influence and alleged nuclear ambitions, counterterrorism.
"Right now you've got a thousand people in government writing policy memos trying to figure out what's going on," said Aaron David Miller, a former U.S. Mideast peacemaker who is now at the Woodrow Wilson Center think tank. "The three-option memo is standard. Option one is Armageddon. The world is falling apart. American interests will be completely threatened
"The third option is: Don't worry, boss, this isn't such a big deal.
"It's the middle option, with respect to American interests, that we have to pay serious attention to," Miller said.
The worst case envisions a rise in extremist Muslim factions in Egypt, Tunisia and even Jordan. The Suez Canal and an adjacent pipeline could be closed, the Egyptian-Israeli peace accord renounced, the U.S.-Egyptian diplomatic and military relationship ended.
Iran could move in to fill the vacuum. That could trigger war between Israel and Iran, perhaps involving nuclear weapons. American influence throughout the region would be greatly diminished.
Most Middle East experts and analysts do not think such a doomsday scenario will happen, particularly with encouraging signs of a peaceful transfer of power in Egypt and with the so-far nonviolent nature of the demonstrations.
There's no return to the status quo
But there still are many signs of stress and potential problems ahead. And, it is clear, there will be no return to the status quo: The U.S. role in the Middle East has probably been altered forever.
"The consequences of instability in Egypt to the United States are really important," said former diplomatic troubleshooter Nicholas Burns, who was the Bush administration's point man on Iran from 2005 to 2008. "The strategic interests of the United States are on the line."
Mubarak's course of saying he will not seek re-election but will not step down immediately or rule out his son as a candidate "guarantees that the demonstrations will continue," said Danielle Pletka, vice president of foreign and defense policy studies at the American Enterprise Institute, a Washington-based think tank. "Their demand is that Mubarak go now, not that Mubarak go in seven months." However, she said, if Mubarak had made the offer earlier that would have defused the crisis.
In his remarks, Obama emphasized that "it is not the role of any other country to determine Egypt's leaders."
Shibley Telhami, a Mideast scholar at the University of Maryland, said it was important for Obama to "lower our tone" and not appear to get directly involved in the leadership change, for fear of creating an unwelcome backlash. "The less we make this about America, the better," Telhami said.
Any period of governmental uncertainty, if Egypt goes through a succession of leaders, or if extremist factions gain the upper hand, could keep tensions across the region high for a long period.
'Egyptian opposition has so many faces'
Also adding to the uncertainty: The protesters are varied and often have conflicting agendas, ranging from students and grass-roots organizers to online activists to the fundamentalist Muslim Brotherhood, which generally wants to form a state governed by Islamic law.The brotherhood is currently banned, but it could gain power in any period of political upheaval. While the Brotherhood claims to have closed its paramilitary wing long ago, it has fought politically to gain power. It has also built a nationwide charity and social network that much of Egypt's population depends on for survival.
"You have to be very careful about instability for a very long period because this is a country where you just have critical problems in food supply and feeding people," said Anthony Cordesman, an expert on the Middle East at the Center for Strategic and international Studies.
All nations in the region, in fact, that aren't big oil-producing states, have problems with poverty and hunger, worries that could be worsened by any destabilizing event, he said. And instability in Egypt could spread to its neighbors.
"In terms of the worst case, the obvious one is that, over time, you see some kind of violent Islamic extremist takeover. The second worst case is that you see the government survive in a form so repressive that basically every passing month creates even more pressure for change and even more anger at the regime and at the United States," said Cordesman, a former director of intelligence assessment in the Pentagon.
A confidential June 2005 U.S. government diplomatic cable, posted online Tuesday by the WikiLeaks organization, showed that the United States has long been concerned that Egypt faced a succession crisis.
Questions about Mubarak's age and health, the cable said, "have made presidential succession a core national issue."
It is not clear how much clout will be wielded by Mohamed ElBaradei, the Nobel-prize laureate who is former director of the International Atomic Energy Agency and who has emerged during the past few days as the leading opposition leader.
"This is so complex because the Egyptian opposition has so many faces," said Peter Morici, a University of Maryland business professor and former chief economist at the U.S. International Trade Commission.
For instance, Morici noted, while ElBaradei is a clear favorite of the West, he has been "quite critical of Egypt's support for the Israeli blockade of Gaza."
Morici said overhanging the whole issue of possible ramifications is the possibility of a tightening of oil supplies by oil-producing states that might be unhappy with the turn of events in Egypt's governance.
With just a 5 percent reduction in production, "you could hit $120 a barrel." That could torpedo a still fragile U.S. economic recovery, he said.