Editor's note: M. Steven Fish is a professor of political science at the University of California, Berkeley. Matthew Kroenig is an assistant professor of government at Georgetown University and a research affiliate at the Belfer Center for Science and International Affairs at the John F. Kennedy School of Government at Harvard University. They are the authors of "The Handbook of National Legislatures: A Global Survey."
(CNN) -- In the past month, we have witnessed a stunning wave of protests that forced Hosni Mubarak, the Egyptian strongman, from the presidential mansion.
What comes next? Does Egypt have a shot at lasting democracy, or is it fated to slide from one form of authoritarianism to another?
The answer may depend less on the behavior of the Egyptian military or the Muslim Brotherhood -- groups that have generated much concern in the West -- than on a factor that has been the subject of much less attention: the strength of Egypt's national legislature.
This week a judicial council is expected to complete a draft of the post-Mubarak constitution in preparation for elections scheduled to be held in September. Its choices about how to distribute power among the branches of government hold the key to Egypt's political future.
If there is one thing Egyptians have been united and consistent in demanding, it is democracy. Protesters risked -- and in many cases sacrificed -- their lives not for the sake of theocracy or more efficient dictatorship. Instead, an end to autocracy and decisive movement to self-government have been their overriding demands.
Egyptians have learned from long, bitter experience that rule by a powerful executive, unchecked by a potent legislature, begets abuse of power and undermines any semblance of self-government. Egypt's experience is easy to comprehend in a broader global framework.
We recently conducted statistical analyses that show that countries with powerful legislatures are much more likely to make the difficult transition from dictatorship to democracy. It is easy to see why.
In recent decades, democracy's staunchest foe has been overweening executives. Presidents in new democracies are frequently tempted to use their positions to amass ever more authority. Unless they meet resistance from a powerful legislature, executives often establish a virtual monopoly on power. Even executives who originally enjoyed reputations as democrats often turn autocratic.
This dynamic has been on display in Russia under President Boris Yeltsin, in Kyrgyzstan under President Askar Akaev, and in Senegal under President Abdoulaye Wade.
In contrast, where chief executives have been constrained by muscular legislatures, presidents have had less opportunity for mischief. In Indonesia, South Korea, Romania, Lithuania, Benin, and Mongolia, post-authoritarian constitutions vested substantial powers in legislatures, which have resisted executive self-aggrandizement and kept democratization on track.
Unfortunately, the People's Assembly of Egypt -- dissolved by the Supreme Council of the Armed Forces earlier this month -- has long been nearly impotent. In our global survey of the power of national legislatures, Egypt ranks 132nd out of 158 countries.
The Egyptian parliament has lacked many of the powers that legislatures should possess in a democracy, including the rights to conduct independent investigations of the executive, to oversee the army and the police, and to review the president's ministerial appointments.
Egypt's legislature, as it was structured, would never be able to check Egypt's next leader, whoever he or she might be; if it is not completely reconfigured, Egypt will once again be condemned to dysfunctional autocratic rule.
Many Egyptians look to Turkey as a model. Like Egypt, Turkey is a Muslim society that enjoys cultural clout and great economic potential. Unlike Egypt, Turkey also enjoys a vibrant democratic regime.
The key to Turkey's success as a democracy certainly has not been a consistently liberal spirit among its leaders or a quiescent military. Turkish leaders, like leaders in most countries, have often been prone to demagoguery, and the military has frequently meddled in politics.
But Turkey enjoys a crucial advantage: a legislature vested with formidable powers. In our global survey, the Turkish legislature ranks 11th out of 158 countries in the world and first in the Middle East and North Africa. Turkey's constitutional system, with its strong parliament and constrained president, has been the secret to its democratic success.
If Egyptians are to have a chance at a democratic future, their new constitution must confer considerable authority on the People's Assembly, including the right to remove the chief executive from office, question and investigate executive branch officials, oversee the armed forces and the police, and approve or reject Cabinet appointments. Furthermore, the executive must be deprived of the power to issue decrees or appoint members of the legislature.
The details of constitutional provisions are less exciting than the tumult that brought us to this point. But they will determine whether the courageous legions that thronged Cairo's Tahrir Square get what they fought for.
The opinions expressed in this commentary are solely those of M. Steven Fish and Matthew Kroenig.