Haiti, the economy, health care, suicide bombs in Kabul. How tempting it must be for the Obama team to consign Iraq to the back burner.

But, while insufficient attention was being paid, Iran has been cleverly meddling in Iraqi politics in the run-up to the March 7 elections, in ways that could spark new Shiite-Sunni violence. More than 500 parliamentary candidates, including some top Sunni politicians, have been banned from running, in a shady process that was probably encouraged by Tehran.

The events leading up to this ban clearly illustrate the importance of an intense U.S. focus on Baghdad if we really want to withdraw our troops by the end of 2011.

The ban was imposed by a controversial commission of questionable legality, whose leading members have close ties to Tehran. Senior Iraqi politicians say they are uncertain as to how this panel acquired the power to ban candidates, who drew up the lists, or why Iraq's election commission endorsed the ban.

But here's the kicker: The chairman of the Accountability and Justice Commission, Ali al-Lami, is a close political ally of the notorious Ahmed Chalabi.

You'll recall that Chalabi is the man who persuaded the Bush team to invade Iraq. (He had a direct phone link to Dick Cheney.) He also provided the CIA with defectors who supplied faulty intel on Saddam's alleged WMD. Ultimately, U.S. officials fell out with Chalabi, in large part because of his close ties to Tehran.

Many Iraqis believe the ban on candidates is intended to ensure success for Shiite political blocs close to Iran (whose regime has solid experience in vote-rigging). Some Iraqi pols believe Chalabi is setting himself up as a compromise candidate for prime minister, with Iranian support.

There is more to this story, of course, than Chalabi's ambitions of a political comeback. Most of the banned candidates were Sunnis linked to the nationalist, secular Iraqiya coalition, including one of its senior leaders, Saleh al-Mutlaq. They were accused of past or present connections to the banned Baathist party of Saddam Hussein.

But unlike many Sunnis, Mutlaq chose early on to take part in the new Iraqi political process, and he has been a member of parliament for the past four years. How can one now justify banning him — or the current minister of defense, also a Sunni — from running for office?

Prime Minister Nouri al-Maliki endorsed the ban, and other Shiite leaders haven't publicly opposed it.

More to the point, the key Iraqi achievement of the past three years — helped by the U.S. troop surge — was the end of the Shiite-Sunni civil war, along with the Sunnis' decision to stop boycotting elections and seek their rights via the ballot.

The candidate ban doesn't rule out Sunnis' participation, but it will lessen their clout and convince them that they won't get a fair shake. And the ban won't renew the civil war, but it could provoke more violence.

Already, al-Qaida-style terrorists are seeking to weaken the Shiite-led government with preelection bombings.

The ban also leaves the clear impression that, behind the facade of Iraqi politics, Iran pulls the strings.

Which brings us back to the need for the Obama team to pay close attention. If these elections take place with full Sunni participation, they will mark a Middle East milestone — a shift in power achieved by a fair ballot, not by a rigged process or coup.

Iraq's politics are just beginning to cross sectarian lines, as many voters tire of religious parties. If the White House wants to leave behind a modest success story, it must work hard to see that this process is not derailed.

The U.S. ambassador in Baghdad, Christopher Hill, achieved much in the Balkans and Asia, but he lacks Mideast experience.

Vice President Joe Biden has been trying to moderate the ban, with no success yet. Time is short, and U.S. influence is waning. A more intense behind-the-scenes effort is needed, now.