Cambridge, Mass.

HOSNI MUBARAK’S promise this week to initiate constitutional reform in Egypt and then step down at the end of his presidential term in September did little to mollify the anger of the demonstrators protesting his rule. Many protesters seemed to agree with the assessment of the opposition leader Mohamed ElBaradei that it was “a trick” intended to buy time. With the regime-sponsored ugliness now engulfing Tahrir Square, demands for Mr. Mubarak’s immediate resignation have grown only more urgent, and the risk of a violent conclusion appears to have grown.

But there may still be a chance to effect the “orderly transition” that Secretary of State Hillary Rodham Clinton has called for. Paradoxically, it requires that Mr. Mubarak stay on, but only for a short time, to initiate the election of an entirely new Parliament that could then amend all the power out of the presidency or even abolish it.

This would no doubt disappoint those who want to put Mr. Mubarak on the next plane to Saudi Arabia, but there are two risks associated with his leaving so abruptly. The first is that the demonstrations might diminish or dissipate, leaving Mr. ElBaradei and his coalition trying to negotiate with the military or Vice President Omar Suleiman without the force of the crowds behind them.

The second risk stems from the Egyptian Constitution, which gives the power to dissolve Parliament and call new elections only to an elected president. Mr. Mubarak’s successor, as an acting president, would be specifically prohibited from getting the parliamentary elections under way. A new Parliament is crucial to democratic reform, because only Parliament has the power to defang the Egyptian presidency, stripping it of its dictatorial powers through constitutional amendment. The current Parliament  bought and paid for by Mr. Mubarak’s National Democratic Party  is not fit for that task.