A new national poll indicates that Sen. Elizabeth Warren enjoys a widening lead over former Vice President Joe Biden in the race for the Democratic presidential nomination — though another recent survey showed Biden holding the top spot.

Warren, the progressive senator from Massachusetts, grabs the support of 28 percent of Democrats and independent voters who lean toward the Democrats in a survey released Thursday by Quinnipiac University. Biden stands at 21 percent in the poll, with populist Sen. Bernie Sanders of Vermont at 15 percent.

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In Quinnipiac’s previous survey – conducted prior to the Oct. 15 fourth round Democratic debate – Warren had a slight 30-27 percent edge over Biden. But her advantage was within the poll’s margin of error. Sanders, the independent senator from Vermont who’s making his second straight White House bid, was at 11 percent.

Quinnipiac’s new survey showing Warren with a clear lead outside the sampling error stands in stark contrast to a national CNN poll conducted by SSRS released a day earlier that suggested Biden at 34 percent, with Warren a distant second at 19 percent and Sanders at 16 percent. The former vice president’s 15 percentage point lead was his largest since April in CNN polling.

During the spring and summer Biden remained the unrivaled front-runner in the Democratic 2020 battle, but then Warren surged and has been tied with the former vice president in many national and early primary and caucus voting state polls this autumn.

South Bend, Ind., Mayor Pete Buttigieg grabs 10 percent support in the new Quinnipiac poll, with Sen. Kamala Harris of California at 5 percent and Sen. Amy Klobuchar of Minnesota at 3 percent. According to Klobuchar’s campaign, their candidate has now reached the polling threshold and qualifies for the next debate, which will be held next month in Georgia.

No other candidate in the record-setting field of Democratic presidential contenders topped 1 percent in the poll.

"Former Vice President Joe Biden slips, Senator Elizabeth Warren steadies, Senator Bernie Sanders gets his groove back, and Mayor Pete Buttigieg breaks back into double digits," Quinnipiac University polling analyst Mary Snow said in a statement.

The survey indicates Biden is still viewed as the candidate who has the best chance of winning against President Trump in the 2020 election. But his electability has deteriorated, from a high of 56 percent days after he declared his candidacy in late April, to 42 percent now.

Thirty percent of those questioned say Warren has the best policy ideas, topping the rest of the field. And Sanders is viewed as the most honest Democratic White House contender, at 28 percent.

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Among the nearly three-quarters of those polled who said they either watched October’s debate or paid close attention to news stories about it, 26 percent said Warren did the best job, followed by Buttigieg with 17 percent, Biden with 12 percent, Sanders at 11 percent, and Klobuchar at 8 percent. When asked who did the worst job in the recent debate, 15 percent said Biden and 11 percent said Rep. Tulsi Gabbard of Hawaii.

"Despite coming under attack at the debate, Senator Elizabeth Warren was viewed as doing the best job, followed by South Bend Mayor Pete Buttigeig, which may have helped his standing in the primary,” Snow said. "Last week's debate didn't help Vice President Joe Biden.”

The Quinnipiac University poll was conducted Oct. 17 - 21, with 1,587 self-identified registered voters — including 713 Democratic voters and independents who lean toward the Democratic Party, questioned by live telephone operators. The survey’s margin of effort for Democratic primary questions is plus or minus 4.6 percentage points.