WASHINGTON — After an Oval Office sit-down on Tuesday did nothing to move Republican Senate leaders off their hard line against a Supreme Court nomination, Democrats pulled out another weapon in the heated election-year fight: Donald Trump. In a White House meeting that lasted less than an hour, Senate Majority Leader Mitch McConnell, R-Ky., and Judiciary Committee Chairman Chuck Grassley, R-Iowa, told President Barack Obama that any confirmation process during a presidential campaign would politicize the court.