In many elections, there's a pivotal moment that appears to signal potential doom for one party or another. For the Democrats and presumptive nominee U.S. President Joe Biden, there have been several of these moments in the past three weeks alone — and the election is still more than four months away. 

The party was already in turmoil after Biden faltered in the first presidential debate last month against his Republican rival, former president Donald Trump.

Biden, who is 81 and the oldest presidential candidate in U.S. history, has struggled to put that performance behind him — despite a number of appearances, news interviews and a press conference — and he's facing calls to step aside for a younger and more dynamic candidate.

Now, there are questions about how Biden's campaign will take on Trump politically after he survived an assassination attempt at a Pennsylvania rally Saturday.

The Democrats are now in a tricky position, especially with Republicans more galvanized than ever in their support for Trump. Quelling internal division over Biden is one thing — sorting out how to proceed while balancing tone and scrutiny following the shooting may determine the outcome of the election.

"The more Democrats can make this election a referendum on Donald Trump rather than a referendum on Joe Biden's fitness to serve another four years, the better off they will be," said Steven Webster, an associate professor of political science at Indiana University.

WATCH | Emotional standing ovation for Trump at Republican National Convention:

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Former U.S. president Donald Trump — with a bandage on his ear — received an emotional standing ovation on the first night of the Republican National Convention just two days after an attempted assassination. Earlier in the day, Ohio Sen. J.D. Vance was announced as Trump’s running mate.

Biden on a mission

Biden says he has no intention of leaving the ticket, and he's on a mission to prove he's a firebrand capable of leading the country for another four years.

In contrast to his June 27 debate performance, Biden was punchy and energetic in a scripted speech at the NAACP national convention in Las Vegas Tuesday. 

That followed an interview with NBC Nightly News anchor Lester Holt Monday evening, where he faced questions about his mental acuity — something he insisted is "pretty damn good." 

Biden reiterated his track record as president and said he should be judged on that. 

But that doesn't necessarily assuage concerns within his party at a time when Trump is riding a swell of Republican support following the attempt on his life and the announcement of his vice-presidential candidate, Ohio Sen. J.D. Vance. 

'Strong and wrong beats weak and right'

The New York Times reported Tuesday that a prominent House Democrat, Rep. Adam Schiff of California, who's running for a seat in the Senate, privately told his supporters at an event on Saturday that the party will suffer significantly in all races on election day if Biden remains on the ballot. 

It's a stronger tone than Schiff has taken publicly, but it echoes concerns raised by party members (at least 19 House representatives and one senator) and fundraisers, including actor George Clooney. 

Bruce Heyman, the former U.S. Ambassador to Canada under Barack Obama, also sees Biden's candidacy as a liability. 

The president, he said in a Tuesday interview with CBC Radio's The Current, was already trailing Trump in key swing states, and his debate performance only made matters worse. 

Heyman believes Biden is a competent leader, but the former ambassador says he's frightened by the idea that "strong and wrong beats weak and right," a phrase he credited to former Democratic president Bill Clinton.

Trump, despite having his ear grazed by a bullet in Saturday's attack, has tried to demonstrate his strength, even stopping to pump his fist in the air to a cheering crowd as Secret Service agents hurried him off stage. He then showed up on the first night of the Republican convention with a bandaged ear.

Biden, meanwhile, has been dogged by footage showing him struggling to answer questions during the debate and confusing the names of world leaders and his own vice-president in public appearances since then. 

Internal pressure

Despite all the negative attention, Webster says the only way Biden won't be at the top of November's ballot is if he withdraws himself.

The Indiana University professor says the president has enough delegates behind him to secure the nomination, even if a growing number of party members want a different candidate.

Webster said it would take pressure from Democratic heavyweights like Obama and former House Speaker Nancy Pelosi for Biden to pull himself out of the race. 

There is some indication that at least one of them is making efforts to get Biden off the ticket, with Politico reporting Monday that Pelosi has been working behind the scenes since the debate to do just that.

WATCH | Biden on whether his messaging could've played a part in inciting violence: 

Biden questioned about political rhetoric after Trump assassination attempt

U.S. President Joe Biden has called for unity following the assassination attempt of rival Donald Trump, but in an interview on NBC News he addressed the role his messaging could have had in inciting violence.

Clock ticking for Biden to woo voters

For now, public calls for Biden to withdraw have quieted somewhat following Saturday's shooting, which left one attendee dead and two others injured. Secret Service snipers also killed the suspected gunman.

Both candidates have cautioned that the heated rhetoric during the election campaign needs to cool off. 

Trump is no stranger to incendiary rhetoric, however, he has vowed to change the tone of his convention speech, slated for Thursday night, to talk about unity.  

And Biden told Holt he was wrong to tell donors to "put Trump in the bull's-eye," during an event in the days ahead of the assassination attempt, though he said he wouldn't back down on telling the truth about his opponent. 

Webster says voters are more swayed by opposition to one candidate, which is why Democrats have tried to provoke fears about the prospect of another Trump presidency. 

"Put simply, an angry voter is a loyal voter," he said.

But that's where it gets complicated for the Democrats now, because Webster says they don't want to appear as though they're playing politics with the attempted assassination of Trump. 

"But at the same time, Democrats still want to push their message that Donald Trump is a threat to American democracy, and that he would be dangerous if given another four years in the White House," said Webster, the author of the book American Rage: How Anger Shapes Our Politics.

Pollster and political strategist Frank Luntz, on the other hand, says it's time for Biden to put more effort into selling his vision for the future rather than criticizing Trump. 

He says Trump already has a base that's excited to vote for him and only needs to convince Republican voters to turn out on election day, Nov. 5. 

"That's not the case with the Biden campaign," Luntz said in an interview with CBC News Network's Power and Politics. "The Biden voters are demoralized." 

He says that if Biden is indeed still in the race next month, Democrats will need "one hell of a convention" to garner support for the president, energize their voters and persuade them to show up at the polls. 

"I don't know if that's possible in these 110 days between now and the election," he said.

WATCH | Why Biden needs to focus on his base, not his opponent: 

This pollster says Biden only has 1 re-election option left

Pollster and communications strategist Frank Luntz says U.S. President Joe Biden needs to stop focusing on his opponent, Donald Trump, and persuade his voters to get a base just as energized as the Republican Party.