NEW YORK (AP) — President Joe Biden this week took a huge step toward achieving a hallmark legislative accomplishment. After months of arduous negotiations, the Senate voted to begin work on the bipartisan infrastructure bill that the president has declared was nothing less than evidence that government itself still worked. But the triumph was shadowed by the surging coronavirus that has forced the restoration of mask guidelines, imperiled the nation’s economic recovery and threatened Biden’s political standing as his party prepares to defend its ultra-slim margins in Congress.