"We cannot tolerate a president who decides that he is going to write law from the Oval Office," argues congressman Steve King. He's part of a faction of Republicans who have brought US government to a standstill after rejecting Obama's national budget reforms. But is shutting down the government an acceptable form of dissent? Or is it, as Thomas Mann from Brookings Institute think tank argues, the political equivalent of "holding a gun to someone's head to get what you want"? As the government slips into a debt-ceiling crisis, former Republican congressman Tom Davis fears that party tensions are beginning to "jeopardise the whole economic system; not just for this country, but for the world".