The top Democrat and Republican in the U.S. Senate joined forces in a rare moment of unity on Thursday in an attempt to pass $40 billion in aid for Ukraine, only to be stymied by a single Republican lawmaker: Sen. Rand Paul. Faced with the prospect of an extended delay for the package that passed the House of Representatives on Tuesday, Senate Majority Leader Chuck Schumer and his Republican counterpart, Mitch McConnell, sought to move forward on the aid package only to be blocked by Paul, a longtime fiscal hawk who objects to the amount of spending proposed. The stalemate has threatened to delay passage of the measure into next week. Late on Thursday, Schumer moved to limit debate on the bill, which could set up an initial procedural vote on Monday. But it was not clear whether leaders were still trying to negotiate a deal that would further speed the bill along.