From Radio Free Europe, Robert Coalson writes about the incentives for Russia regarding sanctions on Iran for its nuclear program. He concludes that the threat of Iran to Russia is minimal, but notices a whole lot of incentives for Russia in a nuclear armed Iran, especially if it leads to war:
And that remote danger is made even more unlikely by repeated U.S. and Israeli declarations that a nuclear-armed Iran is "unacceptable." The refusal of the United States to pull the military option off the table means the worst-case scenario for Moscow, in the event talks fail, is not a mushroom cloud over Kuban but seeing Washington become bogged down in yet another military involvement with the inevitable further sapping of its strength and prestige. The facts that oil prices would also likely skyrocket under such a scenario and that Moscow would emerge as a "reliable energy partner" are probably also not causing Kremlin strategists to lose any sleep.
Unless Russia attempts to heat up the situation before the election, I think that the chances for war probably depend on who wins. If McCain wins, the Russians will believe (probably correctly) that McCain will rush into a war in Iran, and they will try to provoke him. If Obama wins, there's probably less of a chance that they'll try something like that, though I'm not sure that I think the chance is that much lower.