On Tuesday, Mr Biden gave a speech about the impact of former president Franklin D Roosevelt and his own plans for office, at a rally in Warm Springs, Georgia.
“Time and again, throughout our history, we’ve seen charlatans, the con men, the phony populist, who sought to play on our fears, appeal to our worst appetites, and pick at the oldest scabs we have for their own political gain,” Mr Biden said in what appeared to be a reference to the president.
The Democratic nominee then quoted Pope Francis, saying: “In a recent encyclical, Pope Francis warns us against this phony populism that appeals to ‘The basest and most selfish instincts.’
“He goes on to say, ‘Politics is something more noble than posturing, marketing, and media spin. These sow nothing but division, conflict, and a bleak cynicism.’
“He said, ‘For those who seek to lead, we do well to ask ourselves, why am I doing this? Why? What is my real aim?’”
The former vice president added: “Pope Francis asked questions that anyone who seeks to lead this great nation should be able to answer. And my answer is this: I run to unite this nation and to heal this nation.”
Following the Democratic nominee’s speech, the Twitter account @Trumpwarroom, which is managed by the Trump campaign, shared the portion of the speech where Mr Biden said: “Why am I doing this? Why? What is my real aim?”
Joe Biden: “Why am I doing this? Why? What is my real aim?” pic.twitter.com/pNPfzirGjO
— Trump War Room - Text TRUMP to 88022 (@TrumpWarRoom) October 27, 2020
The tweet did not include the context for the former vice president’s comments and made it appear like Mr Biden had become confused during his speech.
President Trump and his campaign have repeatedly attempted to frame Mr Biden, 77, as losing his cognitive abilities and prone to getting lost in a train of thought.
In response, Mike Gwin, Mr Biden’s deputy rapid response director, accused the Trump campaign of “attacking Joe Biden’s faith”.
Mr Gwin tweeted: “@TrumpWarRoom is attacking @JoeBiden by...deceptively editing a clip of Biden quoting an encyclical by Pope Francis.
“Why do they keep attacking @JoeBiden's faith?”
— Mike Gwin (@MichaelJGwin) October 27, 2020
Mr Trump has repeatedly praised conservative Christian groups in speeches and interviews over the last four years, and has attempted to position Mr Biden as being against Christianity.
During a rally for evangelicals earlier this year, Mr Trump said that his “administration will never stop fighting for Americans of faith,” while at an event in Ohio in August, Mr Trump said that Mr Biden, who is catholic, is “against God”.
The president received a majority of the white evangelical Christian vote in 2016, but a poll released by the Pew Research Centre earlier this month showed that his support among Christians has fallen.
The poll found that Mr Trump’s support among white Catholics has dropped by 7 per cent since July, while it has fallen by 6 per cent among white Protestants.
Although support for the president from white evangelical Protestants is still overwhelmingly in his favour, the amount of evangelicals telling Pew they would vote for him has dropped from 83 to 78 per cent since August.
On 3 November, Mr Biden is hoping to become the first Democratic presidential candidate to win Georgia since Bill Clinton in 1992.
An Atlanta Journal-Constitution poll of likely voters published on Monday found Mr Biden leading Mr Trump by 47 to 46 per cent in the state.
The Democratic nominee’s running mate Kamala Harris also visited Atlanta last week, as the pair attempt to take the state President Trump won by five percentage points in 2016.