One of the U.S. Congress’s first acts of 2015? Trying to redefine what counts as full-time work, from 30 hours a week up to 40. It’s part of the latest attempt by Republicans to alter Obama’s signature healthcare law, the Affordable Care Act, and has already passed the House of Representatives. But it has also had the perhaps unexpected effect of putting the divide between full- and part-time workers front and center in American politics.