Obama will likely be as helpless before a crackdown by the Iranian regime as Eisenhower was re: Hungary in 1956, Johnson was re: Prague in 1968, and Bush senior was re: Tienanmen Square in 1989. George W. Bush, it should remember, did nothing about Tehran's crackdown on student protesters in 2003 or about the crackdown on reformist candidates, which excluded them from running in the 2004 Iranian parliamentary elections, or about the probably fraudulent election of Ahmadinejad in 2005. It is hard to see what he could have done, contrary to what his erstwhile supporters in Congress now seem to imply. As an oil state, the Iranian regime does not need the rest of the world and is not easy to pressure. So Obama needs to be careful about raising expectations of any sort of practical intervention by the US, which could not possibly succeed. (Despite the US media's determined ignoring the the Afghanistan War, it is rather a limiting factor on US options with regard to Iran.) Moreover, if the regime succeeds in quelling the protests, however odious it is, it will still be a chess piece on the board of international diplomacy and the US will have to deal with it just as it deals with post-Tiananmen China.
But McCain, Graham, and undoubtedly Holy Joe will have to prove themselves as stupid as Sarah Palin, Sean Hannity or Glenn Beck -- because that's how they roll.