(This is the 20th edition of our power rankings of Democrats most likely to get their party’s presidential nomination in 2020.)

CNN  — 

There are – still! – 20 candidates running for the Democratic presidential nomination. But, at the moment, it looks like a two-horse race.

Those two are former Vice President Joe Biden and Massachusetts Sen. Elizabeth Warren who, in a series of recent polls, increasingly appear to be separating themselves from the rest of the field.

Biden is averaging 28.8% in the Real Clear Politics polling average of all national surveys, while Warren is at 18.3% – almost 2 points clear of Vermont Sen. Bernie Sanders (16.5%).

Warren has been on the rise for several months now, buoyed by massive crowds at her events, positive press coverage of her various policy proposals and solid performances in the first three debates.

Meanwhile, Biden has been under siege – facing questions about his past record, his age, etc. – almost since he entered the race. Still, his numbers have remained strikingly resilient.

There is obviously still time for other candidates to challenge this top two. (Keep an eye on Pete Buttigieg, the mayor of South Bend, Indiana, who may be a sleeper pick to win the Iowa caucuses.) But, for the moment, it’s Biden, Warren and then everyone else.

Below are our picks for the 10 candidates most likely to end up as the Democratic nominee when this is all said and done.

10. Julián Castro: There was a real debate between the two of us if Castro should even be on this list. We decided to keep him on, but it’s pretty clear last week’s debate hurt him. Castro went after Biden, and voters didn’t respond kindly. His unfavorable ratings are up, and Castro’s still at only about 1%-2% in the polls. The good news for Castro is he already has qualified for the next debate. (Previous ranking: 10)

9. Amy Klobuchar: Yes, the Minnesota senator made the stage for the September debate and she’ll be on stage again when the candidates debate in the CNN-sponsored October debate. But, aside from that, it’s hard to find much positive news for Klobuchar. Her performance in Houston felt somewhat desperate as she tried to land a one-liner to create a viral moment and boost her in the race. She wound up sounding more like a Borscht Belt comedian than a presidential candidate. (Previous ranking: 8)

8. Andrew Yang: The unconventional candidacy of this businessman seems to be working – well, working well enough to get him up to 4% in the latest NBC News/Wall Street Journal poll. That was good enough for sixth place in a field of 20 candidates. Given that the name of the game for the lower tier candidates at this point is to keep making debates, Yang’s doing well. He’s also got a fundraising and polling base that many don’t. (Previous ranking: 9)

7. Cory Booker: Booker was quite good again in the third debate. And, as was the case after his first two debate performances, it appears not to have moved the polls in his direction at all. Booker leaned into questions about Biden’s competency after the debate, although he hasn’t kept that drumbeat up. The New Jersey senator needs an angle in this race – and he still hasn’t found one. (Previous ranking: 6)

6. Beto O’Rourke: We’re unsure whether O’Rourke taking his candidacy nationally will help his cause. He doesn’t seem to have received much of a polling bounce since calling for much stricter gun control. Still, O’Rourke appeared to be well received by voters following last week’s debate. When 20 people are running for president and the top tier candidates are taking a lot of oxygen, differentiation helps. (Previous ranking: 7)

5. Pete Buttigieg: There are some signs that Buttigieg’s spade work over the past few months in Iowa are paying off, although he still lags behind the likes of Biden and Warren in the state. Buttigieg continues to play it very safe in the debates, refusing to mix it up with the candidates polling higher than him. Presumably, that will need to change as the fall wears on. He has already exceeded expectations in the race, but now the hard work of pulling votes from his main competitors begins in earnest. (Previous ranking: 5)

4. Kamala Harris: Harris remains the type of candidate (black, prosecutor, etc.) who could break out in a Democratic primary. We saw that when she challenged Biden for the lead after the first debate in a number of polls. Since that point, though, it’s been all downhill for the junior senator from California. Harris has slumped to the single digits, as Warren has risen. The fundamentals of Harris’ candidacy are still there, though we’re reminded of fundamentals-strong Marco Rubio, who could never quite put it all together. (Previous ranking: 4)

3. Bernie Sanders: Bernie’s support appears to have hit a bit of a ceiling as Warren has moved past him in recent weeks. The question going forward for Sanders is if he has a second act or another gear. He has been singing the same song since he began running for president back in 2015, and has built a considerable following as a result. But he has struggled to grow his coalition beyond those hardcore supporters. Can he find a way to do it now?(Previous ranking: 3)

2. Elizabeth Warren: The senior senator from Massachusetts keeps rising in the polls. More Democratic primary voters say they are enthusiastic about her than any other Democrat. Warren’s debate performances have been universally well received. The question is whether she can start making a connection with black voters, who make up a substantial part of the party. Of course, the bigger question may be whether Warren wins Iowa, which doesn’t have many black voters. If she can, Warren may be on her way to winning nationally. (Previous ranking: 2)

1. Joe Biden: Biden’s performance in the September debate was his best yet – in the first hour. In the debate’s second hour, the former vice president flagged badly; his answer on reparations was a total debacle. The debate was, in many ways, indicative of Biden’s campaign more broadly. There are moments where he looks like the for-sure nominee and other moments when he appears to be teetering on total collapse. Biden needs to find more balance in the coming weeks and months as the race tightens and he is challenged more directly by those below him in the polls. (Previous ranking: 1)