If aserioussituationhangsby athread, itmeansthatevenaslightchangecandecidewhat willhappenand that abadresultsuch asdeath,failure, etc. islikely:
千钧一发，岌岌可危，危在旦夕The mayor'spoliticalfuturehas beenhangingby athreadsince thefraudscandal.欺诈丑闻爆出后，市长的政治前途岌岌可危。