Despite protests across Russia sparked by last December's fraud-filled Duma (parliament) elections, Vladimir Putin is preparing to return to the presidency this May. Will Putin replay his 2004-2008 approach to Iran, during which Russia negotiated the S-300 air defense system contract with Tehran? Or will he continue Russia's breakthrough in finding common ground with the United States on Iran seen under President Dmitriy Medvedev, who tore up the S-300 contract? While coordinating more closely with Washington on Iran during the Medvedev administration, Moscow did not and has not closed the door to engagement with Tehran. In 2010, Russia voted for new, enhanced sanctions against Iran at the United Nations Security Council (UNSC). Nevertheless, Moscow and Tehran have remained engaged diplomatically, and their relations have stabilized and begun to recover from their winter 2010-2011 low point. At the same time, Russia continues to insist that Iran comply with its commitments under the Nuclear Non-Proliferation Treaty (NPT) and cooperate fully with International Atomic Energy Agency (IAEA) inspectors. However, Russia is wary of pushing so hard on compliance lest Iran entirely abandon its treaty obligations and walk out of the NPT. In February 2011, Moscow began to oppose another round of UNSC sanctions, and in July 2011 put forward a "step-by-step" initiative coordinated with other Permanent Members of the Security Council and Germany (the so-called P5+1). The Moscow approach offered Tehran a gradual reduction in sanctions in return for improved cooperation with the IAEA in monitoring Iran's nuclear enrichment program. Putin's resentment of U.S. power and suspicion of American motives will make for frostier atmospherics between Moscow and Washington. Nonetheless, mistrust of Iran will continue to outweigh Putin's misgivings about the United States. Everything else being equal, the United States will always be more important to Russia than Iran. Most Russian experts now believe that Iran is advancing toward a military nuclear weapons program-though it has not made a final decision to go all the way-and a ballistic missile program to accompany it. Russia sees these programs as a threat to its interests. Moscow's decision to toughen its approach to Iran on the nuclear issue is likely to remain the basis of Russian policy in the period ahead, so long as the U.S.-Russia "reset" does not totally collapse, especially if Iran does not move toward greater cooperation with the IAEA. Russia's looming domestic and external challenges will strengthen the inclination to continue some variant of reset, even if through Putin's clenched teeth. Russian experts warn that a serious fraying in U.S.-Russia relations might cause Moscow to tilt back toward Tehran. The record on the S-300 contract, however, suggests that any rollback in Russian support for sanctions will depend mostly on whether Iran decides to cooperate more fully with the IAEA in clarifying Iran's nuclear enrichment program and moving toward verifiable restraints on its enrichment activities. On regional issues, however, Russia and Iran will continue at least to appear to pursue neighborly engagement with each other. The Arab Spring has pushed forward overlapping but not identical challenges and opportunities to the positions of both countries in the Middle East, including how to deal with Syria. The impending American withdrawal from Afghanistan has raised the prospect that Russia and Iran may once again have to partner closely in resisting Taliban threats to their regional equities, as they did before 9/11. Engagement has historically been Moscow's default setting for dealing with Tehran. Russia's current step-by-step initiative appears designed to continue engagement, while underscoring Russia's potential role as a mediator between Iran and the international community. the future of Russian-Iranian relations.