Supporters of Democratic presidential candidate Bernie Sanders (I-VT) left a mock caucus at Iowa’s Drake University in protest after Democratic presidential candidate Elizabeth Warren (D-MA) won and Sanders failed to meet the event’s “viability threshold.” With voting in Iowa’s statewide caucuses just a week away, colleges held simulations of the events across the state Monday night. NBC News campaign embed Ben Pu covered the Drake University mock caucus, and reported that after the first round, only Warren and former South Bend, Indiana Mayor Pete Buttigieg exceeded the 15 percent viability threshold. “!!! Only Buttigieg and Warren are viable. Supporters are...