To outside observers, Egypt appears to be sliding toward a new authoritarianism, this time under an Islamist ruler.

The current struggle is over a referendum on a new constitution, and whether it's a prelude to a future political takeover by Islamist groups. Egypt's President Mohammed Morsi, a man of the Muslim Brotherhood, says the document must be put to a two-stage vote, on Dec. 15 and Dec. 22, to speed the transition to full democracy.

Morsi's opponents believe the document contains dangerous loopholes. They also say the president's illegal methods of forcing the vote prove that his real aim is to consolidate power.

The outcome will help answer a critical question: Can pluralist democracy flourish in Arab countries, where Islamist movements are far better organized than newer, secular or moderate Muslim parties? Although the trend in Egypt is bleak, the outcome isn't yet a foregone conclusion. It will depend in large part on the smarts of the opposition and the West's use of its economic leverage.

To calculate the odds, here are five things you need to know about what is happening in Egypt and how the United States can help.

1. First, some good news: Egypt is not Iran, nor will its political development look anything like that country's. Sunni Egypt's history and culture are very different from that of Shiite Iran, where clerics play a greater societal role.

Moreover, Iran's Ayatollah Khomeini overruled Shiite doctrine when he decreed that a supreme cleric could rule his country as a stand-in for the still-absent messiah. Whatever happens in Egypt, Sunni clerics will not exercise direct political rule.

2. Some bad news: The Brotherhood does want to Islamicize Egyptian society and culture (although nowhere near as much as the smaller Salafi parties, which, unlike the Brothers, want to introduce harsh Islamic criminal penalties). In 2007, Morsi proposed a party platform that called for a clerical review board to vet laws.

Equally worrisome, the Brotherhood's instincts are not democratic. Long forced to operate underground and from prison, Morsi and his colleagues are eager to cement their power. They reversed themselves on a pledge not to contest more than 30 percent of parliamentary votes or to run a presidential candidate. Rather than negotiate further with the opposition on the draft constitution, Morsi issued a presidential decree putting himself above the courts, which were about to nullify the constitutional assembly. Organized Brotherhood cadres chanting "God is great" beat and tortured opponents who were demonstrating against Morsi's extrajudicial move.

3. However, all is not lost. The Constitution is not as bad as it has been painted. It does not incorporate sharia law, as hard-line Salafi Muslims demanded, keeping the vaguer wording of the 1971 constitution, which says laws must not contravene the principles of sharia.

The danger lies in the many loopholes in the draft, which will permit the next Parliament to define the role of religion in the state and the extent of presidential power. Thus, the real key to Egypt's future lies in who wins the next parliamentary elections, in February. Another victory by Islamists could cement their power, while opposition gains could prevent that.

4. Much depends on whether Egypt's political opposition can get its act together. Though adept at demonstrations, its leaders have quarreled among themselves while failing to create strong parties or movements. Nor have they set up organizations outside the major cities that could rival the cadres of the Muslim Brotherhood and Salafi groups.

There's no doubt the constitutional referendum will pass. (The public is tired of the turmoil.) However, Egyptians are souring on the Islamists. They have yet to deliver on their economic promises, and they have annoyed generally easygoing Egyptians with their attempts to impose Islamic cultural restrictions, such as forcing bars and restaurants to close by 10 p.m.

The popularity of the president's Freedom and Justice Party is already slipping: It won 47 percent of the first parliamentary vote, in 2010, and Salafi parties won more than 20 percent. But Morsi won only 51.7 percent of last year's presidential ballots. Now the opposition has finally unified against Morsi's constitutional gambit. If it got serious about organizing voters, it could do well at the polls.

5. Which brings us to the role of the United States and its allies. Grateful for Morsi's help in quieting Gaza and maintaining Egypt's peace treaty with Israel, the Obama administration has been restrained in its critique of the constitutional struggle. In private, however, U.S. officials should be delivering strong messages to both sides.

To the Egyptian president, the word should be that Western aid, loans, and investment won't be forthcoming if the regime clamps down on the opposition or interferes with training and funding for non-Islamist parties. To opposition groups, the message should be: Get your act together, define your goals, and we will support a free and open political process. Within the next few months, we will know whether that process can work.