Going into this election cycle, Michelle Obama had nothing to prove. She’d passed the test long ago, with a 2008 Democratic National Convention speech that proved to be a turning point in her career as First Lady. But this year she somehow one-upped herself, delivering groundbreaking speech after groundbreaking speech and quickly becoming one of Hillary Clinton’s most important surrogates — the power player her campaign deployed when it needed to sway opinion in its candidate’s favor.