Updated at 12:30 p.m.
House Majority Whip James Clyburn offered an emotional presidential endorsement of Joe Biden on Wednesday, just three days ahead of South Carolina's Democratic primary — a contest that could be make-or-break for the former vice president's campaign.
"I've known for a long time who I was going to vote for. I'm voting for Joe Biden. South Carolinians should be voting for Joe Biden," Clyburn said at an event in North Charleston.
"We know Joe," the South Carolina Democrat said in a video put out by the Biden campaign. "But more importantly, he knows us."
Clyburn also referenced his late wife in speaking of the former vice president.
"We often talked about the leadership of this country, and there is nobody who Emily loved as a leader in this country more than she loved Joe Biden," he said at the North Charleston event.
Clyburn, 79, is one of the most popular and influential African American politicians in the state. With long-established ties to Biden, his support does not come as a surprise but rather suggests Biden needs all the help he can get to shore up support from black voters, who make up nearly two-thirds of the Democratic electorate in South Carolina.
Biden's campaign is betting heavily on a South Carolina victory to carry him through to victories in the March 3 Super Tuesday contests. His performance so far in the early contests has been lackluster: fourth place in Iowa; fifth place in New Hampshire; and a distant second place in Nevada.
During Tuesday night's debate in Charleston, Biden confidently declared: "I will win South Carolina." When pressed whether he would continue his campaign if he doesn't come in first in the state's primary, Biden repeated his prediction he would win.
Biden joined Clyburn at the Wednesday event and praised him as a "extraordinary leader" and said his reputation extends beyond South Carolina. "Jim has a voice of powerful, powerful moral clarity."
Without mentioning Vermont Sen. Bernie Sanders, the front-runner in the primary, Biden said there is talk about "revolution" but he argued, "what the country is looking for is results" and cited his role in passing Obamacare.
Virtually all polling in South Carolina has Biden leading, but his once seemingly insurmountable double-digit lead has eroded to single digits in the closing weeks of the race. The latest CBS News/You Gov poll has Biden leading the field with 51%, followed closely by Sanders with 44%.
An emotional Clyburn said he was "fearful" about the state of the country and pointed to Biden as the candidate to lead the party. "I know his heart, I know who he is, I know what he is. This country is at an inflection point."
NPR's Juana Summers and Asma Khalid contributed to this story.