But Beto O’Rourke, who pushed incumbent Ted Cruz hard in the senatorial race in Texas, is also being urged to throw his hat into the ring after an impressive showing in the deeply conservative state.
Mr Biden has not yet confirmed he intends to run in two years time – but that has not stopped him being installed as the early frontrunner, with the survey putting his support at 29 percent in a Reuters/Ipsos Election Day poll.
Senator Bernie Sanders, an independent who made an unsuccessful run for the Democratic nomination in 2016, finished second in the hypothetical field with 22 percent.
The rest of the poll was tied between Senators Cory Booker of New Jersey, Elizabeth Warren of Massachusetts and Kamala Harris of California.
All of the Democrats fared well in a popular vote hypothetical matchup against US President Donald Trump.
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Before a single dollar has been spent on election ads or campaign rallies, the poll found Biden scored best in a hypothetical matchup, beating Trump 51 percent to 39 percent in the popular vote.
The poll found Sanders, Mr Booker and Ms Harris would also defeat Trump nationally if the election were held today.
Trump did the best against Mr Booker, losing by only four percentage points in the hypothetical popular vote.
In 2016, Democrat Hillary Clinton won the popular vote by nearly three million ballots but lost the presidential election to Trump, who won the state-by-state Electoral College vote.
Joe Biden has been installed as the early Democratic frontrunner (Image: GETTY)
Opinion polls at this early a stage tend to be largely dominated by those with the most widespread name recognition.
Several polls after the 2014 congressional midterm elections found Jeb Bush, who ultimately lost his bid for the Republican nomination, to be the front-runner. Few polls even included Trump.
On the Republican side, 65 percent of Tuesday’s midterm voters said they would renominate Mr Trump to represent their party. Another 11 percent said they would prefer Vice President Mike Pence and 12 percent said they did not know who should be the nominee.
The Reuters/Ipsos Election Day poll was conducted online on Tuesday and based on responses from 38,196 people who voted in 37 states. The poll is ongoing and will be updated as the vote is tallied.
The hashtag #beto2020 is trending on Twitter after Beto O’Rourke impressed in Texas (Image: GETTY)
I think there are many people in the Democractic party who can defeat President Trump
Mr Biden, who opted not to seek the Democratic Party’s nomination in 2016 because his son was terminally ill, addressed the subject of a possible 2020 tilt during an address delivered at Chatham House last month.
He said: “I think there are many people in the Democractic party who can defeat President Trump.
“Not a single aspiring candidate that I can think of, and I am not one of them at this point, does not have a better understanding of foreign policy than President Trump.
“I think there are any number of potential candidates seeking the nomination, from Kamala Harris and a full range of people in my party who would pursue a much more enlightened foreign policy than President Trump.”
Kamala Harris is another possible nominee (Image: GETTY)
Mr Biden, 75, has said he will make a decision about whether to run by January.
Meanwhile, Mr O’Rourke, who was narrowly defeated by Mr Cruz by a margin of 50.9 percent to 48.3 percent, representing the best Democratic showing in the state in 20 years, is being urged to consider a bid of his own, with the hashtag #beto2020 trending on Twitter.
During his concession speech, the 46-year-old from El Paso said: “I believe in you, I believe in Texas and I believe in this country.
“I’m as inspired, I’m as hopeful as I’ve ever been in my life.
Bernie Sanders ran Hillary Clinton close in 2016 (Image: GETTY)
“Tonight’s loss does nothing to diminish the way that I feel about Texas or this country.”
Bookmakers Coral made Ms Harris their early favourite, rating her chances of winning the nomination at 5-1, closely followed by Mr O’Rourke and Mrs Warren at 6-1.
Mr Biden was rated at 8-1 and Mr Sanders at 10-1, with former talk show host Oprah Winfrey at 20-1 and Michelle Obama at 33-1.
Mr Trump, unsurprisingly, was the overwhelming favourite for the Republicans at 2-1, with current Vice-President Mike Pence at 8-1, and Nikki Haley and Paul Ryan at 20-1.