(This is the sixth edition of our monthly power rankings of Democrats most likely to get their party's presidential nomination in 2020.)

That's the reality of the moment as the Democratic Party begins to ramp up for what will almost certainly be the largest presidential field in modern memory. O'Rourke seems to be everywhere these days -- such as meeting with former President Barack Obama -- and is, without doubt, the candidate everyone else thinking about the 2020 race has (at least) one eye on.

O'Rourke has that thing that every candidate -- Democrat or Republican -- wants: organic energy. He generates excitement everywhere he goes -- and is being urged to run by activists from all over the Democratic base.

He's the flavor of the moment, no question. But can he turn that initial excitement into a full-fledged campaign and sustain momentum over the next year-plus?

Below, our rankings of the 10 people most likely to wind up as the Democratic nominee against President Donald Trump in 2020. We do this every month, so if your preferred candidate isn't on the list (or isn't as high as you'd like) stay tuned!

10. Kirsten Gillibrand: There was some question as to whether the junior senator from New York was game for 2020. It now seems that she is seriously contemplating a bid. On the face of it, Gillibrand has a lot going for her. She has the most anti-Trump record of any senator. She has the megaphone that the New York media has to offer and easily won reelection there last month. Yet in a crowded field, Gillibrand may have some trouble standing out. (Previous ranking: Not ranked)

9. Julian Castro: He's running! Well, basically. The former San Antonio mayor : He's running! Well, basically. The former San Antonio mayor tried to get a jumpstart on the pack this week when he announced he was forming an exploratory committee -- and would make a final decision by January 12. He's almost certainly in, but questions remain as to whether there is room for both young Texas Democratic firebrands, Castro and O'Rourke, in this race. (Previous ranking: 7)

8. Sherrod Brown: You want someone with a long progressive record and a history of winning in the Midwest, then let me introduce to senior senator from Ohio. Brown has one of the : You want someone with a long progressive record and a history of winning in the Midwest, then let me introduce to senior senator from Ohio. Brown has one of the most liberal voting records of any senator. He just easily earned another Senate term from Ohio voters, despite all other major statewide Democratic candidates falling short. A Democrat winning Ohio's 18 electoral votes would be a major Electoral College boon, and Brown's electability could sell with Democrats desperate to beat Trump. Still, Brown's a white male in a party that is becoming less white and was intent on nominating women in 2018 . He may not be a great fit. (Previous ranking: 9)

7. Amy Klobuchar: We probably had the Minnesota senator : We probably had the Minnesota senator ranked too highly last month , given the obvious hurdles she has to clear -- namely that she isn't a well-known figure nationally (at all) and has to show she can raise money to compete with some of the top-tier folks. Still, Klobuchar's serious and steady approach to politics and policy -- not to mention her Midwestern roots -- could make her a player in the Iowa caucuses. (Previous ranking: 4)

6. Bernie Sanders: The case for the independent senator from Vermont is fairly simple. He won over 40% of the 2016 primary vote, and the party has, if anything, moved closer to his leftist positions since that election. Sanders also has an infrastructure in place and name recognition to stand out from a crowded field. We wonder though if time has passed Sanders by. He just : The case for the independent senator from Vermont is fairly simple. He won over 40% of the 2016 primary vote, and the party has, if anything, moved closer to his leftist positions since that election. Sanders also has an infrastructure in place and name recognition to stand out from a crowded field. We wonder though if time has passed Sanders by. He just came in third in a straw poll with just 13% among progressive MoveOn.org activists. Sanders won 78% in that same straw poll in 2016. Additionally, other fresher faces may be better able to claim the outsider label in 2016. It was the ability to seem outside the establishment that propelled Sanders in 2016 more than anything else. (Previous ranking: 6)

5. Elizabeth Warren: The last month has made clear just how much damage Warren did to her chances with a : The last month has made clear just how much damage Warren did to her chances with a badly botched attempt to put to rest questions about her Native American heritage . The Massachusetts senator seems to be struggling to regain that momentum, although it's important to note -- as Politico reported recently -- that she has already begun the laborious process of building a 2020 campaign machine . That, plus the more than $12 million she has in the bank to spend on a presidential bid, mean Warren may be down, but she's not out. (Previous ranking: 2)

4. Cory Booker: New Jersey's junior senator manages to keep moving up our list. Part of that is attributable to the clear yearning for young faces among Democratic activists. (Booker is only 49.) Part of that is that a tireless work ethic that seems to be paying dividends. When noting how much money Booker raised for New Hampshire Democrats, state party chairman Ray Buckley said Booker is "the best friend New Hampshire Democrats had in 2018." Booker, who is black and the former mayor of Newark (50% black), could be in a prime position to win black voters, who will make up 20%-25% of the primary electorate. Booker though has his flaws. But some progressives view him as a dreaded "neoliberal," and some may see him as a bit over-dramatic ( : New Jersey's junior senator manages to keep moving up our list. Part of that is attributable to the clear yearning for young faces among Democratic activists. (Booker is only 49.) Part of that is that a tireless work ethic that seems to be paying dividends. When noting how much money Booker raised for New Hampshire Democrats, state party chairman Ray Buckley said Booker is "the best friend New Hampshire Democrats had in 2018." Booker, who is black and the former mayor of Newark (50% black), could be in a prime position to win black voters, who will make up 20%-25% of the primary electorate. Booker though has his flaws. But some progressives view him as a dreaded "neoliberal," and some may see him as a bit over-dramatic ( see his "Spartacus" moment ). (Previous ranking: 5)

3. Joe Biden: Everything the former vice president has said and done over the past year makes it very clear that he is planning on running for president. The latest? His assertion that : Everything the former vice president has said and done over the past year makes it very clear that he is planning on running for president. The latest? His assertion that he is the "most qualified" person in the country to be president . And the vast majority of polls we've seen put Biden at or very near the top of the field. The question is, can her maintain that frontrunner status in a party that seems less than interested in picking a septuagenarian white male as its next national face? (Previous ranking: 3)

2. Beto O'Rourke: The guy just lost a Senate race. And yet, here we are with O'Rourke in second. It's tough not to pay attention to a candidate who seems to have energized Democratic activists in Iowa, : The guy just lost a Senate race. And yet, here we are with O'Rourke in second. It's tough not to pay attention to a candidate who seems to have energized Democratic activists in Iowa, won the MoveOn.org straw poll (showing he has some oomph with grassroots progressives), has won plaudits from Obama and is making moves toward running. Oh, and we don't think it's going to be particularly difficult for O'Rourke to get noticed given he just raised nearly $80 million for a Senate bid . Still, folks really shouldn't get ahead of themselves. Being ranked second in what will be a very large field is a long way away from actually winning. Will Democrats actually nominate a white man in 2020? Can O'Rourke actually stand the spotlight that is sure to come if he runs? We may just find out soon enough. (Previous ranking: 10)