Can you hold a dialogue with an Iranian regime that blatantly steals an election as the world watches? Should we help the Iranians who are protesting that election?

These are the questions confronting President Obama as the riveting drama in Iran continues, with hundreds of thousands of Iranians marching in the largest demonstrations since the country's revolution, objecting to the election results.

Graphic YouTube videos of police beating demonstrators hit hard at the emotions. (Western correspondents have been expelled from the country or banned from covering the demonstrations.)

Some conservative politicians and pundits are demanding that Obama back the demonstrators. Otherwise, says the Wall Street Journal's Bret Stephens, "a future president may have to apologize to Iranians for Mr. Obama's nonfeasance," just as Obama apologized for U.S. involvement in the overthrow of an elected Iranian leader in 1953. Stephens and others think Obama should reject the election results and publicly endorse opposition leader Mir Hossein Mousavi.

Sorry. That would be the kiss of death for the opposition's cause.

This is true even though there's scant doubt that the election was hijacked. The key evidence: Iran's paper ballots are tabulated by hand, and then the data is painstakingly entered into computers. There is no exit polling. The count, say experts who have witnessed previous elections, never takes less than 24 hours.

Yet in this election, the regime's TV station named Ahmadinejad the winner around 90 minutes after the last polls closed. The results from half of the 39.2 million ballots were announced in four hours, and the final results were made public in a little more than 12 hours. The reported percentage - nearly two-thirds for Ahmadinejad - never changed.

Despite the astonishing turnout of more than 80 percent - and the fact that high turnout has historically favored reformers - Ahmadinejad got around seven million more votes than in 2005. The signs of fraud are endless, but these will suffice.

The best analyses I've seen contend that the regime picked the margin before the balloting and went with it irrespective of the actual tally. There's no way to know for certain, because the ballots have been kept secret and observers weren't allowed to monitor the counting.

So what we see in Iran is an explosion of anger among those fed up with Ahmadinejad's West-baiting foreign policy and economic malfeasance, his repression of youth and women, and the injustice of this vote.

Make no mistake: Ahmadinejad still has a solid base among the rural poor, Iranian nationalists, and those who benefit from the regime, such as the Revolutionary Guard military forces. And, of course, he has the support of Iran's supreme leader and real power, Ayatollah Ali Khamenei.

It's possible that the Iranian president's tally was close to his challenger's. However, Khamenei - who dislikes reformers and has old scores to settle with Mousavi - apparently decided not to take any chances, so the victory margin was made enormous. Clearly, Khamenei was not prepared for the extent of the reaction. Contrary to some claims, the protesters reflect a far greater swath of society than north Tehran's well-to-do.

But an open endorsement by Obama of their protest would give Ahmadinejad just the excuse he is seeking to crush these protests. If the Iranian leader could claim this was another U.S.-backed "color revolution" aimed at regime change, like those in Ukraine and Georgia, it would make a crackdown easier to justify.

The troubled history of U.S.-Iranian relations would make many Iranians wary of American intervention. Nor would many regime opponents who want reform, not revolution - including Mousavi - be likely to welcome an American embrace.

So I believe Obama is correct to stress that the United States won't meddle in the election. But it is also vital for Obama to stress - as he finally did in the past two days - that America and the world have deep concerns about the election. He should keep repeating that "the world is watching."

As for his pledge to continue to pursue "tough, direct dialogue" with Iran, this policy will inevitably be affected by how the regime deals with the election challenge. Obama was correct to offer Iran this choice, but if the protests flare into violence and virtual civil war, the prospects for dialogue will become moot.

Obama will have to reassess his policy as the drama continues. But the struggle for justice must be waged by the people of Iran.