Having tossed out a poorly explained assertion that Tehran has little attractive ideology to offer the world in its campaign to lead a challenge to the U.S.-centric world political system, I would like to underscore the distinction between an "ideology" and a "policy position." An ideology, I would argue, is a broad construct, much more substantive than a simple policy position. Ideologies include capitalism, communism, socialism, and Khomenei's version of Shi'i clerical dictatorship. I would maintain that this ideology offers little attraction to the rest of the world, even its mistreated Shi'a. Be they Pakistani, Iraqi, Lebanese, Bahraini, or Saudi, Shi'a in general do not appear to find the idea of submitting to Khomenei's particular vision as very attractive. (Comments from those who have more expertise on this issue would be more than welcome.)
Policy is another matter, and Tehran offers the disadvantaged of the world some (potentially) very attractive policies. In a unipolar world, the big guy of course gets blamed for everything that goes wrong, and indeed when you strive to be Numero Uno, you deserve it. Tehran is the world's most open critic of the U.S.-centric global political system. Tehran may not have a very inspirational ideology, but it does offer a clear policy: replace unipolarity with...whatever. More specifically, it has a policy of rejecting Israeli military dominance over the Mideast and Israeli exceptionalism (e.g., only Israel is allowed nuclear arms, only Israel is allowed to maintain occupation forces outside its legally recognized borders).
Tehran becomes a significant player for free simply because it is essentially has a monopoly on that policy line of "resistance." This position is "free" because it does not actually have to do anything except assert the policy position and accrue the benefit of being the only actor in the world with the guts to "say no."
What Washington needs to understand is that this puts Tehran in a fundamentally passive position - its dissident stance is significant only to the degree that Washington takes such a hard-line counter-position as to make Tehran look like Robin Hood to Washington's King John. If King John had been just a bit more generous with the poor and had been a bit more willing to share power with the nobles, he could have pulled the rug out from under his opponents and been a popular king. An Obama calling for Arab democracy and insisting on the rights of Palestinians leaves Tehran rejectionists out in the cold, talking to themselves. An Obama protecting individual Arab dictators against the interests of the Arab people or kowtowing to an extremist and expansionist Israeli faction, however, hands to Tehran rejectionists a degree of global political influence they could never obtain for themselves. Tehran's future is in the hands of Washington, and so far Washington is giving Tehran exactly what it wants: an easy target.