As Kamala Harris races to capture the Big Mac Voter, the Trump campaign is doubling down on its demand for proof that she worked at McDonald's in college.“Why won’t they just provide real documentation and proof?” Trump campaign spokesman Steven Cheung said in an email to the Daily Beast. “The onus is on them. What does she have to hide?"Donald Trump has attacked the Democratic presidential nominee’s McDonald’s street creds as fake, accusing her of lying about having worked there as a college st