Joe Biden's policies always faced high hurdles with Republicans, but one Democratic senator balking at the US president's voting rights bill has signalled that the bulk of the ambitious White House agenda is under threat. Biden succeeded earlier this year in ramming through a massive spending package to help the economy recover from the coronavirus pandemic. - Balancing act -Manchin's obstinacy, and his illusory hope of a bipartisan breakthrough, has earned harsh criticism from within the party. Fellow moderate Kyrsten Sinema of Arizona has also shown an unpredictable appetite to break with party leadership. But even going that route, Biden would need to keep people like Manchin and Sinema on board, while not losing the support of more progressive Democrats.