WASHINGTON – Massachusetts Sen. Elizabeth Warren has taken over the top spot in several recent national presidential primary polls as candidates prepare to debate Oct. 15.

Most national polls since the end of September have found Warren – not former Vice President Joe Biden – leading the pack, but by relatively narrow margins.

Biden had led in almost every national poll, usually by double digits, going back to 2018. But Warren has come out on top in four of the past five and six of the past 10.

And she recently pulled ahead in the RealClearPolitics average, a frequently cited polling benchmark. Though she is in front of Biden only by 0.2%, it marks the first time Biden has not held the lead in the race's RCP average since the site began comparing the polls in December.

The most recent poll to place her at the top was released Tuesday by Quinnipiac University. That poll found her ahead of Biden 29%-26%. Sen. Bernie Sanders of Vermont came in third at 16%. Among those who described themselves as "very liberal," Warren led Biden 38%-26%, and among the "somewhat" liberals she led 37%-23%. Biden led among moderate and conservative Democrats 35%-22%.

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"Warren maintains her strength in the Democratic primary, which has been consistently growing since the start of her campaign. This poll confirms her status as a co-frontrunner with Biden," said Quinnipiac University Polling Analyst Tim Malloy.

The poll found that Warren held narrow leads with both men and women and that she had a 12-percentage-point lead with white voters. Biden was favored by black voters 36%-20% and by voters over 65 by a 41%-26% margin.

The survey was conducted Oct. 4-7 from among 1,483 self-identified registered voters with a margin of error of plus or minus 3.1%.

Warren also has performed well in the early primary states that can be key to securing the nomination. Last month, a Des Moines Register/CNN/Mediacom Iowa Poll found her leading in the first-in-the-nation caucus state, and a Monmouth University poll put her narrowly ahead of Biden in New Hampshire. A Suffolk University/USA TODAY Network Poll released on Sept. 24 placed her just 4 points behind Biden in Nevada, the third state where primary voters will cast their ballots.

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Biden maintains a comfortable 41%-12% lead over Warren in South Carolina, the fourth state on the primary calendar, according to a recent Fox News poll.

The former vice president's drop in the polls comes as President Donald Trump and his personal attorney Rudy Giuliani have mounted a public campaign accusing Biden of impropriety in Ukraine during his time in office. Trump's effort to pressure Ukraine to dig deeper into the matter has sparked an impeachment inquiry.

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Tuesday's poll from Quinnipiac shows that voters approve of the impeachment inquiry 53%-43% and that 45% think Trump should be removed from office while 49% do not. The margin had been 37%-57% in a Quinnipiac poll before the inquiry launched.

Only 34% said they approved of the way Trump has responded to the impeachment inquiry, compared with 57% who disapproved. But 43% agreed with the president that it was a "political witch hunt," while 51% said it was a "legitimate investigation."

Though Trump has said his effort to push Ukraine to investigate Biden was motivated by a desire to battle corruption rather than taint a political opponent, only 33% of voters bought that explanation, and 48% said he was out to hurt a rival. Twenty percent weren't yet certain or thought both reasons were true.

Polls have consistently found that Democratic voters care more about picking a candidate in 2020 who can defeat Trump than any particular policy issue. When asked whom they would vote for if the election was held today, Quinnipiac found that both Warren and Biden would beat the incumbent president – Biden by a margin of 51%-40% and Warren by a margin of 49%-41%.

Trump indirectly acknowledged Warren's rise in the polls in a tweet Tuesday in which he called on his 2016 Democratic opponent Hillary Clinton to "enter the race to try and steal it away from Uber Left Elizabeth Warren."

Speaking to House Republicans in Baltimore last month, Trump said Warren had "emerged from the ashes. And now it looks like she can beat Sleepy Joe (Biden)."

"He has no idea what’s going on," Trump said.

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