There have been several national polls conducted since the third round of the Democratic presidential debates. There are variations in the support for each candidate from survey to survey, which makes it difficult to make sense of the race, but the bottom line is the fat lady hasn’t sung yet.

The post-debate polls show only three candidates in double digits: former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and Sens. Bernie Sanders Bernie SandersSirota reacts to report of harassment, doxing by Harris supporters Republicans not immune to the malady that hobbled Democrats The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election MORE (I-Vt.) and Elizabeth Warren Elizabeth WarrenOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds On The Money: Half of states deplete funds for Trump's 0 unemployment expansion | EU appealing ruling in Apple tax case | House Democrats include more aid for airlines in coronavirus package Warren, Khanna request IG investigation into Pentagon's use of coronavirus funds MORE (D-Mass.). This has been the case for several weeks.

Recent national polls indicate that Biden leads the field, although the size of his lead varies from poll to poll — but emerging state polls show Warren could pull ahead.

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Sen. Kamala Harris Kamala HarrisTexas Democratic official urges Biden to visit state: 'I thought he had his own plane' The Hill's Campaign Report: Biden on Trump: 'He'll leave' l GOP laywers brush off Trump's election remarks l Obama's endorsements A game theorist's advice to President Trump on filling the Supreme Court seat MORE (D-Calif.), former Texas Rep. Beto O'Rourke Beto O'RourkeJimmy Carter says his son smoked pot with Willie Nelson on White House roof O'Rourke endorses Kennedy for Senate: 'A champion for the values we're most proud of' 2020 Democrats do convention Zoom call MORE and South Bend, Indiana, Mayor Pete Buttigieg Pete ButtigiegBillionaire who donated to Trump in 2016 donates to Biden The Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice MORE all had their moments in the sun, but they failed to capitalize on their early momentum. Harris has dropped 8 points since July, according to a new poll by NBC News and The Wall Street Journal.

All three candidates have languished in single digits for weeks but are still in play if they light a spark or manage an upset victory in Iowa or New Hampshire. The other candidates still in the race have never registered significantly in the polls and are hanging on by their fingernails.

The NBC/Wall Street Journal poll indicated that only 9 percent of Democratic primary voters have a solid commitment to their candidate of choice. Biden, Warren and Sanders may be the frontrunners, but only a minority of their supporters are enthusiastic about their favored candidate.

A good stiff breeze could disturb the pecking order at the top of the Democratic contest.

Biden has led the pack since he entered the race, but his advantage is not secure. His lead in the national polls has declined steadily in the last few months. The Real Clear Politics poll index had him as high as 40 percent back in May but his vote has declined to 30 percent. His lead in the early delegate selection states of Iowa and New Hampshire, where all candidates have more visibility, is even more precarious.

Warren is the candidate on the move. She has been consistently effective without any flubs in the three Democratic debates. Last week, she got great visibility with a massive anti-corruption rally in New York City and received the endorsement of the progressive Working Families Party, which supported Sanders in 2016.

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Two polls captured her momentum. The NBC/Wall Street Journal poll has her at 26 percent — within spitting distance of frontrunner Biden (31 percent) and way ahead of Sanders, at 14 percent. Warren has gained 6 points since July, while Sanders support has been stagnant.

A new survey of Democratic caucus-goers by CNN and the Des Moines Register tells a similar story. While Warren polled at 22 percent and Biden 20 percent, in reality, they are in a statistical tie there. Meanwhile, Sanders lags at 11 percent. Since June, Warren has gained 6 points, while Biden has declined by 3 percent and Sanders has dropped by 5 percent.

Warren could easily secure a lead in the polls soon. While Biden’s vote has declined since he got in the race and Sanders’s support has stagnated, Warren has gained steadily.

Her vote is growing as she catches up with both men in name recognition. This means she has more room for growth than the other two. Her increased visibility is almost entirely positive. The only way to stop her is for Biden and Sanders to go after her.

Pundits have noted Warren’s rise in the polls and opined that the race has become a two-person confrontation between her and Biden. That is premature, but there are signs that Warren has eaten into Sanders’s young progressive base and cut his candidacy off at the knees.

In the NBC/Wall Street national survey, Warren has a clear advantage over Sanders among the voters who fueled his insurgent campaign against Hillary Clinton Hillary Diane Rodham ClintonBloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close Trump pledges to make Juneteenth a federal holiday, designate KKK a terrorist group in pitch to Black voters MORE in 2016.

At 36 percent, Warren has almost twice as much liberal support as Biden and Sanders do at 19 percent each. Warren now has almost as much support from millennials as Sanders. Warren even leads Sanders among voters who want bold policy proposals rather than mild ones from the Democratic presidential candidates.

In the Iowa survey, a third (32 percent) of the Democrats who caucused for Sanders in 2016 now support Warren. Only a quarter (25 percent) of the 2016 Sanders supports are still with the Sanders.

With Biden dominating the field among moderate and conservative Democrats and Warren winning liberals, where does that leave Sanders?

There are reasons for Warren’s rise at Sanders’s expense. To some Democrats, she is Bernie without the baggage. Warren — like Sanders — supports “Medicare for all” and the Green New Deal. But Warren insists she’s a capitalist and disdains the socialist label. The Sanders of 2020 is remarkably similar to Bernie 2016, but voters value freshness and prefer original programming over reruns.

Elections are not simply battles over policy proposals. Like it or not, presidential politics is about popularity, and Warren is now better liked than Sanders and Biden. In the Iowa survey, three of four potential caucus-goers (75 percent) have a favorable opinion of her, which makes her the most popular candidate in the field.

Warren is an immediate threat to Sanders and a proximate threat to Biden. The two men will need to stop Warren’s momentum. That means drawing a clear line between their candidacies and Warren’s.

Biden could make the case that Warren's heart is in the right place but Medicare for all is a pie-in-the-sky proposal that will increase taxes on working families — one that's impossible to implement and difficult to defend against President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE next fall. Sanders could argue that his proposals are bolder and more transformative than the plans of his colleague from Warren.

Polls are simply a snapshot of the race. There is still room for twists and turns on the long and winding road to the Democratic presidential nomination. So, pay attention and don’t jump to any conclusions. There will be lots of thrills and spills on the way to Milwaukee.

Brad Bannon is a Democratic pollster and CEO of Bannon Communications Research. He is also the host of a radio podcast “Deadline D.C. With Brad Bannon” that airs on the Progressive Voices Network. Follow him on Twitter @BradBannon.