Call him the anti-Ahmadinejad.

In preparation for his speech at the U.N. General Assembly today (the same day as President Obama), the new Iranian president, Hassan Rowhani, has conducted a diplomatic offensive of astonishing proportions, including an exchange of letters with Obama, network interviews, tweets, and an op-ed in the Washington Post.

Rowhani’s message: Iran is a responsible international actor with no intention of seeking a nuclear bomb. Subtext: No more bombastic denunciations of America and the West or Holocaust denials at the U.N. podium or other forums.

“He recognizes that statements (Mahmoud) Ahmadinejad made on Israel and the Holocaust caused Iran immense damage,” says Iran expert Karim Sadjadpour of the Carnegie Endowment. “He is making a conscious effort to be the anti-Ahmadinejad.”

Skeptics will argue that Rowhani offers a change of style, not substance. Israeli Prime Minister Benjamin Netanyahu has called him a “wolf in sheep’s clothing.” However, while a dose of skepticism is healthy, there’s growing evidence that Rowhani is offering more than cosmetic changes.

We will know more soon: His U.N. speech, which is expected to include proposals to address concerns about Tehran’s nuclear program, could be the prelude to the first top-level U.S.-Iran talks since Iran’s revolution in 1979. In the meantime, here are six reasons why this diplomatic push may have legs.

1. The economic sanctions imposed by the United States and United Nations on Iran’s oil sales and money transfers have worked. “The sanctions have been breaking the back of the Iranian economy and consumers,” says Haleh Esfandiari, director of the Middle East program at the Woodrow Wilson Center for International Scholars. “The cost of living is going up day by day; a tomato that costs $1 today will cost $1.50 tomorrow.” The Iranian administration is concerned that people might riot over food prices.
2. Rowhani appears to have the backing of the supreme leader, Ayatollah Ali Khamenei, for his diplomatic efforts, at least for now. Some experts believe the economic impact of sanctions convinced Khamenei; others think he may have more trust in Rowhani, the consummate insider, than in previous presidents. While the ayatollah’s ideology is rooted in deep anti-Americanism, Sadjadpour thinks he might countenance détente with the Great Satan, if not rapprochement.
3. Rowhani insists Iran isn’t seeking weapons of mass destruction “including nuclear weapons, nor will we ever.” Of course, this leaves unresolved the fact that nuclear experts believe Iran was seeking to build a weapon prior to 2003 and still wants a breakout capacity. But Tehran’s intent will become more clear if talks resume. And Rowhani’s choice of chief negotiator is promising: Mohammad Javad Zarif, the U.S.-educated and pragmatic former Iranian ambassador to the United Nations, who was sidelined under Ahmadinejad.
4. Rowhani understands Ahmadinejad’s threats toward Israel and Holocaust denial badly damaged Iran’s image. He and Zarif have engaged in some fascinating Twitter diplomacy, sending out Rosh Hashanah greetings earlier this month. When Nancy Pelosi’s daughter tweeted that the new year would be sweeter if Iran ceased its Holocaust denial, Zarif responded: “Iran never denied it. The man who was perceived to be denying it is now gone.” Rowhani and Zarif have come under attack from Iranian hard-liners for this Twitter offensive. That may be the reason why, when Rowhani was asked in an NBC interview if he believed the Holocaust was a myth, he punted: “I’m not a historian. I’m a politician.” However, when asked further about Israel, he stated: “We are not … looking for war with any nations.” This message appears to be the bottom line Rowhani is trying to convey.
5. Rowhani seems to recognize that Iran needs better relations with the United States (and its Gulf allies) to calm spreading Sunni-Shiite violence in the region. Right now, Iranian policies are fueling sectarian bloodshed, by backing Hezbollah and arming the Syrian regime, so it’s hard to take seriously Rowhani’s suggestion that Tehran could mediate the Syrian conflict. But the Iranians do share Washington’s interest in curbing a new regional threat from Sunni jihadis, including al-Qaeda, and that could provide the basis for beginning a dialogue.
6. Paradoxically, the U.S. decision not to bomb Syria may have made it easier for Rowhani to negotiate seriously on the nuclear issue, since it indicates that Washington is not bent on regime change – in Damascus or Tehran.

That said, it’s uncertain if Iran will do what’s necessary to convince the world it isn’t bent on building a bomb-making capacity, or that Rowhani will be willing to wait for sanctions relief until Iran proves its good intent.

Still, it’s clear that Rowhani is a leader to be taken seriously, the very opposite of an Ahmadinejad. That’s why his speech is the most eagerly awaited moment at the United Nations today.