For former Vice President Joe Biden a win in this Saturday’s South Carolina Democratic primary is crucial to proving his viability as a candidate, according to John King CNN’s Chief National Correspondent.

Upon entering the race, pundits considered Biden a front-runner and he consistently polled as the leading candidate. However, once voting began, Biden failed to meet expectations. In the first two contests in Iowa and New Hampshire, the former vice president failed to finish in either first or second place and in Nevada he came in a distant second to Sen. Bernie Sanders.

King said Biden’s campaign is hoping a win in South Carolina will prove he has a path to victory. A loss, however, could end it for the former vice president.

“It would be debilitating,” King said during an interview with Boston Public Radio on Tuesday. “You cannot keep coming in third or fourth. He got second in Nevada, which gave him a life line, but it was a very distant second.”

King is CNN’s Chief National Correspondent and anchor of Inside Politics.