Iran: What is the effect of more sanctions on domestic Iranian politics?

A diplomatic resolution to the Iranian nuclear programme is certainly the most desirable outcome. However, it seems that the chances for such a resolution are diminishing by time, to the extent that rumours of a possible US or Israeli air-strike on Iranian nuclear facilities has become a weekly routine in the current media for the past year. The debate over the issue has spanned now more than six years, three of them in which Iran has continued publicly to defy the UNSC Resolution 1696 ban on its uranium enrichment programme. A fourth round of sanctions proposed by members of the six nations has not even been agreed upon despite a year of negotiations. China and Russia have been stalling the approval of further sanctions due to their economic interests with Iran; nevertheless both states have demonstrated some pressure on Iran to comply with UNSC resolutions. Lately, the improvement of Russian-US relations has proven to be productive, as Russia refused to set a delivery date regarding its arms deal to sell the sophisticated S-300 anti-aircraft system to Iran.