President Biden and Republicans in Congress are on a partisan collision course over raising the debt ceiling — the legislatively mandated limit on how much the U.S. can borrow. And the clock is ticking. The $31.4 trillion ceiling has already been reached, so now the Department of the Treasury is using accounting gimmicks to pay the government’s bills. But those maneuvers — what Treasury calls “extraordinary measures” — may only stave off default through early June by the department’s current estimate.