Last week, Human Rights Watch put out a blunt assessment of what the United States has left behind after eight years in Iraq: "Despite U.S. government assurances that it helped create a stable democracy, the reality is that it left behind a budding police state."

Too true. And a striking example of this downhill slide is the recent arrest of Riyadh al-Adhadh, a Sunni doctor known for helping the poor who was recently jailed on terrorism charges.

Dr. Riyadh, as everyone calls him, courageously advocated democracy in the face of Sunni militant threats. Those who know him well believe the charge against him is ludicrous.

Rather, his case appears to be part of an effort by Shiite Prime Minister Nouri al-Maliki to repress and marginalize Sunnis, including elected officials - and to monopolize power. Down that road lie chaos, sectarian war, and the reemergence of Islamic extremists, including al-Qaeda. In other words, the destruction of all that U.S. officials claim to have achieved over the last eight years.

Yet, the administration seems unwilling to use what leverage it still has to prevent this result.

Dr. Riyadh's story is the perfect example of what's gone so wrong in Baghdad. I first met him in 2003 through Col. Joe Rice, a U.S. Army reservist from Denver, who did five tours in Iraq. Rice helped set up local government institutions in Baghdad; he worked with Dr. Riyadh, who lived in Adhamiyah - a Baghdad neighborhood that became a hotbed of Sunni resistance.

But the doctor chose political resistance over violence. Despite death threats against anyone who worked with Americans, he joined the local Adhamiyah council (two of whose members were murdered). Then he ran for office, won a seat on the Baghdad provincial council, and was named council vice president.

"Some people accuse me of working for the Americans," he told me in 2004 in his spartan clinic, where poor patients crowded into the stairwell and hallways. "But I think I must take part in the political process because I want the people to have representation."

He said he had urged Adhamiyah locals not to attack Americans who came to talk to local council members. But he was also bitterly critical of the errors of the U.S. occupation - such as the failure to restore electricity or compensate his neighborhood for war damage.

When Rice invited him and other council members to Denver to see how local governments worked here, the doctor spoke out about abuses at Abu Ghraib prison (before that abuse became a public scandal). His criticism got him in hot water with U.S. authorities in Baghdad and nearly got him arrested. Yet such frankness made the doctor credible in his district.

Could Rice imagine the doctor helping terrorists? I asked him this week, by phone. "No, I cannot," came back the firm reply. "He was in there dissuading them, telling them there was another way. He was part of the solution, not part of the problem."

So why has the Maliki government arrested a doctor who risked his life to work within the system? This question brings us to the heart of the matter - Iraq as a budding police state.

The U.S. invasion of Iraq upended decades of rule by the Sunni minority. Yet for the democratic process to work in Iraq, the Shiite majority must accept a political role for Sunnis, so long as they play by constitutional rules.

Yet, as U.S. troops were leaving Iraq, the Shiite-led Maliki government, fearful of a Sunni resurgence, began arresting Sunni parliamentarians; they also rounded up many Sunnis who had abandoned militancy and fought with American forces. Moreover, the government still refuses to honor a pledge to share power with the Sunni-dominated Iraqiya party, which won a narrow majority of seats in the last elections.

In December, the government arrested Sunni Vice President Tariq al-Hashimi, the leader of the Iraqi Islamic Party, to which Dr. Riyadh belongs. Hashimi was charged with terrorism, based on "confessions" by his guards, who were paraded on state television in scenes reminiscent of the days of Saddam Hussein.

With the government paralyzed, Sunni extremists have reemerged and are trying to reignite a civil war by attacking Shiite civilians. The government's dragnet arrests and questionable charges only fan this fire.

Vice President Biden has been making phone calls to Shiite, Sunni, and Kurdish leaders in Baghdad, urging them to reconcile. But in the meantime, the United States is going ahead with plans to sell F-16s, tanks, and armored personnel carriers to an Iraqi government that may use them in a new police state.

No doubt the White House wants to arm Iraq as a counterweight to Iran. But Maliki has made himself evermore dependent on Shiite Iran by alienating Sunnis and relying on Tehran's support to stay in power.

It's time for a White House rethink. Phone calls are insufficient. While Washington still has leverage - from potential arms sales - that leverage should be used to push Maliki toward the politics of consensus, rather than the politics of sectarian ruin.

One sign that Maliki gets the message would be the release of Dr. Riyadh from jail.