Emily Bazelon, David Plotz, and John Dickerson discuss the first Republican debate, a potential presidential run by Joe Biden, and the state of the #BlackLivesMatter movement a year after Michael Brown’s death.   The Slate Political Gabfest is sponsored by Casper, an online retailer of premium mattresses for a fraction of the price. Casper mattresses come with free delivery and returns within a 100-day period. And get 50 dollars toward any mattress purchase by visiting casper.com/gabfest and using the promo code POLITICAL.   Also by Trunk Club. Answer a few simple questions about your look, style, and size, and receive a trunk full of great looking clothes that fit perfectly and make you look amazing. Only pay for the clothes you keep, and shipping is free. Go to TrunkClub.com/gabfest.   And by Stamps.com. Buy and print official U.S. postage using your own computer and printer, and save up to 80% compared to a postage meter. Sign up for a no-risk trial and a $110 bonus offer when you visit Stamps.com and use the promo code GABFEST.   Join Slate Plus! Members get bonus segments, exclusive member-only podcasts, and more. Sign up for a free trial today atwww.slate.com/gabfestplus.   Twitter: @SlateGabfest Facebook: facebook.com/Gabfest Email: gabfest@slate.com   Show notes at slate.com/gabfest Learn more about your ad choices. Visit megaphone.fm/adchoices