Why this could be the most important week of Joe Biden's political life

Joe Biden is staring down what could be the end of his political career.

The former vice-president's campaign for the Democratic presidential nomination is hobbling toward its do-or-die moment this weekend in South Carolina.

Biden is in desperate need of a win to maintain credibility as a candidate given his fourth place finish in Iowa, his fifth place finish in New Hampshire and his second place finish in Nevada last weekend.

While second place is an improvement, his team had still hoped for a better turnout.

Can he make an impact during tonight's televised debate in Charleston, S.C.? Can he win the primary on Saturday after publicly predicting he would? And can he finally start building momentum based on support from the black community now that a state with a diverse population is about to have its say?

There are signs the 77-year-old is worried it may be too late for his campaign.

Lowering expectations

Biden is lowering expectations ahead of Saturday's vote, backing away from his claim that South Carolina is his "firewall" — the state where his support among black voters would finally come into play and help him secure a win.

During his time as a lawmaker and as vice-president, Biden spent years building ties with diverse communities.

However, during an appearance on CBS's Face the Nation this week, Biden claimed he never used the word "firewall" to describe South Carolina.

"No, it's not a fire — I said I'm going to do well there. And I will do well there, and I will do well beyond there as well," he said, taking issue with the specific word.

But Biden has used that word. In fact, he did so just before the Iowa caucuses earlier this month, as he tried to downplay expectations before that contest.

He argued his surge of support would come later in the nomination race, telling NBC News: "I think I have a real firewall in South Carolina. And then we go into the Super Tuesday states that have a significant number of minorities and African Americans."

Stumble in Iowa

After enjoying a comfortable run where he was seen as the front-runner in the national polls, Biden started to struggle once the actual counting of votes began.

His challenges were on full display earlier this month in Iowa, where his biggest rally ahead of caucus day fell flat.

On an unseasonably warm Sunday afternoon in Des Moines, about 1,100 people crammed inside a middle school gymnasium.

The crowd grew restless when the start time was delayed for unknown reasons, which is not unusual for a political event.

Supporters became increasingly uncomfortable as the temperature in the gym crept up, prompting many to shed layers of winter clothing and to use campaign signs as makeshift fans.

When the preshow finally began, eight speakers took their turn introducing Biden, some with curious messages that didn't seem to energize the crowd.

"America needs Joe Biden a hell of a lot more than Joe Biden needs to be president," said Harold Schaitberger, the general president of the International Association of Firefighters.

Two members of Congress from Iowa, Rep. Abby Finkenauer and Rep. Cindy Axne, urged the crowd to help get Biden elected, in part so they can keep their own jobs in Washington.

"We've got to make sure that we've got the support from everybody in this room to make sure that there is a person at the top of the ticket that will help us keep our seats," Axne said. "That person is Joe Biden."

When you compare that sentiment to some of the themes in other campaigns — for example, the Bernie Sanders slogan "Not me. Us" — it's perhaps not surprising it didn't hit the mark in the gym.

When Biden finally took the stage, his stump speech focused mostly on President Donald Trump.

At times, he yelled in frustration, accusing Trump of stoking division, especially on issues related to race.

'It's like a hostage-taking'

In the audience that day was Chad Rogers, a former Conservative strategist who is now a partner at Crestview Strategy. He'd travelled from Toronto to Des Moines with his friends to see the caucusing process in person.

"It's like a hostage-taking," he said at one point during Biden's event.

In a followup conversation by phone this week, Rogers elaborated on what he'd meant by the comment. He said the Biden bid has morphed into a classic imperial campaign.

While Biden is well liked and people at his events believe they should be there to support him, once you get into the room, no one actually wants to be there and it just doesn't work, Rogers said.

"If that campaign was milk, you'd look at the date and throw it out," he said.

Tall order, even with a win in South Carolina

Obviously, one bad rally doesn't define an entire campaign.

But Biden has been unable to shake off his underwhelming start to the nomination race. While he pitches himself as the best candidate to defeat Trump, he is trailing Sanders in the race for the Democratic nomination, a candidate whose more progressive promises, such as Medicare for All, Biden considers unrealistic.

Sanders is the front-runner in the delegate count so far, and a new poll shows he's gaining ground in South Carolina ahead of Saturday's vote.

According to the CBS News poll, Biden is still holding on to the lead, with 28 per cent support. Sanders is not far behind, picking up momentum with 23 per cent, followed by businessman Tom Steyer in third at 18 per cent.

Perhaps most troubling for the Biden campaign is the poll suggests his support among black voters dropped 19 points since the fall, from 54 per cent to 35 per cent.

There are also signs Sanders is chipping away at that support — he finished second among black voters in the Nevada primary, garnering 27 per cent of the votes to Biden's 39 per cent, according to entrance polls.

Biden's depleted coffers a serious drag on his chances

Saturday's primary is Biden's last test before Super Tuesday, on March 3, when contests are held in 14 different states, including delegate-rich California and Texas.

Even if Biden were able to hang on and win in South Carolina, he would have just three days to try to translate that into gains on Super Tuesday and slow down the momentum of Sanders. That kind of effort could benefit from a flood of ads, but Biden is not among the campaign leaders when it comes to fundraising or spending. 

Still, if Biden is going to have any shot at convincing a lot more voters to pick him on Super Tuesday, he'll need to be able to point to evidence he is capable of galvanizing supporters.

Without a win on Saturday in South Carolina, that becomes nearly impossible.