Sen. Elizabeth Warren and former Vice President Joe Biden are virtually deadlocked in a close race for the Democratic presidential nomination, according to a new national poll out Wednesday from Quinnipiac University.

The poll shows Warren at 27% and Biden at 25% among Democratic voters and independent voters who lean Democratic, and is the first major national poll to show Warren in this strong a position since polling in Iowa and New Hampshire also found the two knotted at the top of the field. Although the difference between the candidates' numbers is within the poll's margin of error, the Massachusetts Democrat's new ranking is the first time a candidate other than the former vice president has topped the pack since Quinnipiac started posing the question in March.

The two candidates also saw change in support from the poll's August results, when Biden was at 32% and Warren was at 19%.

The poll reflects a tightening Democratic race as well as Warren's increasing consolidation of the progressive vote and making inroads among black voters. Her support among that crucial demographic bloc has climbed dramatically in recent months, from 4% in July to 8% in August to 19% now. Biden's support among black voters, meanwhile, has dipped from 53% to 40% over the same time. The numbers signal a potential softening in a key base for Biden's campaign, as well as an ability for Warren to grow support beyond white college-educated liberals.

In the new poll, Warren and Biden are followed by Vermont Sen. Bernie Sanders (16%), South Bend, Indiana, Mayor Pete Buttigieg (7%) and California Sen. Kamala Harris (3%). All other candidates got 2% or lower in the poll.

Two other national telephone polls released since the last round of debates -- from NBC News and the Wall Street Journal, and from Fox News -- found Biden in a stronger position ahead of Warren. But recent surveys taken in early voting states show a two-person top tier forming.

A CNN/Des Moines Register/Mediacom poll released over the weekend found Warren surging in Iowa against Biden, standing at 22% to the former vice president's 20% among likely Iowa caucusgoers. And in New Hampshire, a poll of likely Democratic primary voters from Monmouth University favor Warren over Biden, 27% to 25%.

The Quinnipiac University poll was conducted by telephone September 19 through 23 among a random sample of 1,337 registered voters with a margin of sampling error of plus or minus 3.2 percentage points. The survey includes 561 Democratic voters and independent voters who lean Democratic with a margin of sampling error of plus or minus 4.9 percentage points.