Germany's SPD endorses Schulz as leader and Merkel challenger

By Michelle MartinBERLIN (Reuters) - Germany's Social Democrats (SPD) on Sunday formally endorsed former European Parliament President Martin Schulz as their leader and challenger to Chancellor Angela Merkel in what is set to be a tightly contested national election in September.The SPD has undergone a revival since nominating Schulz in late January, gaining around 10 points in opinion polls and signing up thousands of new members as the 61-year-old focuses his campaign on social justice."The SP