KOBLENZ, Germany-Europe’s leading anti-immigrant and antiestablishment politicians rallied in the Rhineland on Saturday to launch an election year they hope will topple the European Union, displaying a new level of ambition and organization and casting U.S. President Donald Trump as their inspiration. It was the first time that Marine Le Pen, the French nationalist leader vying for the presidency, campaigned alongside Frauke Petry, the most prominent of Germany’s anti-immigrant politicians.