Obama to make White House pitch for Clinton

By Amanda Becker and Luciana Lopez PHILADELPHIA (Reuters) - Barack Obama will add an optimistic pitch on Wednesday to the campaign to elect Hillary Clinton as the first woman U.S. president, as he seeks to hand off the White House to a trusted fellow Democrat and stop Republican Donald Trump. Clinton formally secured the Democratic Party's presidential nomination on Tuesday, coming back from a stinging defeat to Obama in her first White House run in 2008 and surviving a bitter primary fight agai