A co-founder of Facebook is donating $20 million of his fortune to Democratic coffers in a late and likely consequential move to help defeat Republican candidate Donald Trump in the 2016 presidential election. The funds are a surprising infusion of cash from an individual who has never before been active in politics. Dustin Moskovitz, a Silicon Valley entrepreneur with a net worth of more than $10 billion, announced early Friday that he and his wife would make a historically large donation to a half-dozen Democratic groups, including those backing Hillary Clinton. The donations, once issued, will make Moskovitz the third...