With much of the media and political punditry taken up by revelations about Donald Trump’s allegedly inappropriate phone call with the leader of Ukraine, and the decision by Nancy Pelosi to move forward with impeachment, the Massachusetts senator has quietly surged ahead.
What’s more, many observers believe the impeachment investigation could create more headaches for Mr Biden, who Mr Trump asked Ukraine’s Volodymyr Zelensky to investigate for alleged corruption.
There has never been evidence to support long-held accusations by conservatives that Mr Biden inappropriately used his position as vice president to push for the ousting of an allegedly corrupt Ukrainian prosecutor who was investigating an energy firm that employed his son, Hunter.
However, in the days since Democrats said they were proceeding with impeachment investigations involving six committees of the House of Representatives, Republicans have hit back with accusations about Mr Biden and his son that could harm his 2020 run.
“I refer to Warren and Biden as co-frontrunners. I don’t see how you could in fairness do anything but that. Of course the contest is dynamic and could change rapidly,” Larry Sabato, professor of politics at the University of Virginia, told The Independent.
“Biden ought to be very worried about Warren. His argument is basically his electability, and if he loses that, he is going to struggle. Warren’s problem is that loads of Democrats think she’s too far left to defeat Trump.”
Four polls used by the Democratic National Committee (DNC) to determine which candidates qualify for its debates this week gave Ms Warren a lead over Mr Biden in Iowa, the first state to hold a primary or caucus, and in New Hampshire, which is the second. A poll also placed her ahead of the former vice president in another early primary state, Nevada, where voters cast ballots on 22 February.
Meanwhile, a fourth poll carried out by Quinnipiac University gave Ms Warren a lead over Mr Biden nationally, with her on 27 points, him on 25 and Bernie Sanders in a distant third on 16 points. Another poll, carried out by Economist/YouGov, which is not officially counted by the DNC but is well respected, also gave Ms Warren a one-point advantage over Mr Biden nationally, scoring them 27 to 26.
The polling companies point out such a narrow gap is within the margin of error. Nevertheless, there has been a sense that as 76-year-old Mr Biden has been forced to answer questions about his age and mental acuity after a series of less than stellar debate performances, the 70-year-old Ms Warren has barely put a foot wrong.
This week, she supported the move to proceed with an impeachment investigation of Mr Trump, but urged Democrats not to overreach on something so divisive.
“Right now, I’d like to just see us do the Ukraine issue because it is so clear and it is such a clear violation of law,” she told CNN. “The president is asking for help against one of his political rivals and asking a foreign government for a thing of value for himself personally. That’s against the law.”
She has consistently impressed voters with her grasp on policy issues, and showed in three successive debates she was able to display passion when she needed to. A number of pundits believe the Democratic race will turn into a choice between one of the two frontrunners – the centrist Mr Biden, or the progressive Ms Warren.
“It now appears likely to boil down to a two-way contest, one in which Democrats will have to decide whether to go big or go home,” analyst Charlie Cook, founder of the bipartisan Cook Political Report, wrote this week.
“In this case, going big is doing something bold, daring, and exciting but potentially risky – that is, going with Warren. Going home is to a more comfortable, familiar, but not terribly exciting place: Biden. Revolution versus restoration.”
In an indication of apparent concern among some of Mr Biden’s top advisors, The New York Times reported there had been discussions about whether the campaign should start taking money from large donors.
All the other major candidates have sworn off the idea of accepting money from a political action committee, or PAC, but some of Mr Biden’s supporters believe he may need corporate donations to fight off the accusations Republicans are already making about him. All candidates are conscious of the way Democrats have often failed to respond to Republican smears, as in the case of allegations made about Hillary Clinton in 2016, and John Kerry in 2004.
“The vice president is getting hit from all directions,” Mark Riddle, a political strategist who was involved in discussions, told the newspaper.
“A lot of us believe there should be a fair fight. He can hold his own with his campaign in these early states or whatnot, but there’s only so much incoming somebody can take without a response.”
TJ Ducklo, a spokesman for Mr Biden, said he would reject any super PACs that joined the race on his side.
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