Islamists took to the streets of Cairo late last month to call for Islamic law in Egypt. The rally chills any remaining optimism surrounding the Arab Spring.

When Egyptian President Hosni Mubarak resigned six months ago, the White House hailed his ouster as akin to fall of the Berlin Wall. "We can't help but hear the echoes of history -- echoes from Germans tearing down a wall," President Barack Obama remarked.

President George W. Bush agreed. "We live in exciting times and I'm not surprised that freedom continues to march forward," he declared.

Sometimes, however, freedom stumbles. When Iran's shah fell in 1979, there was also initial optimism. "The depiction of him as fanatical, reactionary, and the bearer of crude prejudices seems certainly and happily false," Richard Falk, a Princeton political scientist well-regarded by the Carter administration, wrote of revolutionary leader Ayatollah Khomeini. Richard Cottam, a diplomat and Iran specialist, reported that Khomeini's inner circle was "desirous of relying on the U.S. for Iran's defense." Nine months later, however, reality interceded. Khomeini's supporters sacked the U.S. embassy sparking a hostage crisis which poisons relations to the present day.

In Egypt's revolution, Mubarak's downfall marks not the beginning of the end, but rather the end of the beginning. Decisions made now will reverberate for decades. Speaking on an Arabic satellite channel just days after Mubarak's ouster, Secretary of State Clinton called for "a democratic transition with free and fair elections" while also acknowledging "the end of the road is what matters."

Clinton's realism is welcome. After all, as the Bush administration learned in Palestine and Lebanon, elections do not ensure democracy. Still, it does not appear that Obama has learned the other lesson of the Bush years: Election systems matter.

In the rush to elections in Iraq, for example, Bush acquiesced to a system in which all Iraqis would share a single constituency and vote for party lists rather than individuals. This empowered populist leaders who exploited religious or ethnic divisions rather than debate issues like education and development. Likewise, by prohibiting voters from knowing how individuals fell on party lists, corrupt politicians could shield themselves from public accountability. Iraqis have since sought to rectify these mistakes, but their country continues to pay the price.

In Egypt's case, there is broad consensus among Egyptians about the need for election reform. In a March referendum, Egyptians approved modest changes to reduce the president's term and speed up new parliamentary elections, now scheduled for November. Egyptian democracy activists, however, say that the reforms do not go far enough. After all, Egypt's parliamentary elections are notoriously complex: Two officials represent every district, one of whom must be a farmer or a worker. In elections, higher vote getters are disqualified until both quotas are filled.

Obama and Clinton should side with reformers who want real electoral change. While the White House agrees with most Egyptians that the Muslim Brotherhood should participate in elections, any victory which propels the group to power is inimical to U.S. interests. Sure, suave Brotherhood spokesman promise to embrace democratic principles. So did Khomeini. Hard line Brotherhood preachers give reason for concern: The group eulogized Usama Bin Laden and praised his resistance, and has whipped up sectarian hatred against Egypt's minority Christians. Brotherhood hardliners openly suggest scrapping Egypt's peace treaty with Israel.

It's against this backdrop that the White House should use its leverage to ensure not only free elections, but also those which ensure the checks and balances necessary for democracy.

Egypt experts agree the Brotherhood has a natural constituency of only 25 percent of the population but, at the same time, acknowledge it is the best organized party in the new Egypt.

If Egypt holds elections according to a winner-takes-all system (as in the United States), the Brotherhood might leverage its minority support to achieve a dominating grip on government.

However, if Egypt adopts proportional representation, then even the most fractious and disorganized secular leaders can form a coalition after elections to quarantine or balance populists whose commitment to democracy is tactical and fleeting.

Likewise, the White House should demand that Egypt embrace open lists. Corrupt politicians should not hide behind unconditional American aid. Nor should American tax payers help fund any country afraid to allow international dignitaries to observe elections.

Egypt's revolution may be six months old and its elections another three months away, but decisions about how they shape Egypt's future will be made now. Alas, it appears Obama and Clinton are asleep at the switch.

Michael Rubin is a resident scholar at the American Enterprise Institute in Washington, D.C.