Republican leaders signaled Sunday that any final nuclear deal struck with Iran will face deep opposition in the GOP-controlled Congress. For weeks, Republicans have called for President Barack Obama and his team of U.S. diplomats to walk away from negotiations aimed at curbing Iran’s ability to build nuclear weapons. As top officials entered what they labeled a “decisive” phase of talks with Iran and five other global powers on Sunday, GOP leaders said they doubted a final deal would pass muster with most Republicans. “It’s going to be a very hard sell — if it’s completed — in Congress,” Senate Majority Leader Mitch McConnell (R., Ky.) said on Fox News Sunday. Mr. McConnell said he worried that any deal would still leave Iran capable of producing a nuclear weapon on relatively short notice. “We already know that it’s going to leave Iran as a threshold nuclear state,” Mr. McConnell […]