Democrats to contrast Clinton with Trump's 'dangerous' approach

By Amanda Becker and Luciana Lopez PHILADELPHIA (Reuters) - Barack Obama will highlight Hillary Clinton's judgment and toughness on Wednesday as he seeks to boost her campaign to be the first woman U.S. president, hoping 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 at the party's convention in Philadelphia on Tuesday. Wednesday's convention events will focus on national security,