海角大神

He鈥檚 finally in the pool.

The speculation over whether or not former Vice President Joe Biden would join the crowded 2020 Democratic primary field officially ended Thursday when he released a video declaring his bid for president.

The announcement was almost a formality. From the start of the campaign cycle, the press has treated Mr. Biden 鈥� a five-term U.S. senator and popular two-term vice president 鈥� as though he were already running. He has led most polls against candidates who declared months earlier, including Vermont Sen. Bernie Sanders, and has reportedly lined up big donors and endorsements from key party figures, elected officials, and organized labor.

Yet none of the hoopla ahead of Uncle Joe鈥檚 announcement has stopped the Democratic field from ballooning out of historical proportion. Unlike in 2016, when Hillary Clinton鈥檚 campaign all but cleared the field of contenders, the 2020 race feels like a Democratic free-for-all. Twenty candidates are now gunning for the nomination, including a former tech executive, a self-help author, and a sprinkling of House representatives. Indeed, Rep. Seth Moulton, D-Mass., a former Marine Corps officer on his second term in Congress, felt empowered聽to announce his presidential bid聽the same week as Mr. Biden.

Why does everyone seem to think they have a shot, even with Mr. Biden in the ring?

The answer, mostly, is that 2020 is not 2016. In a post-Trump world, where someone with no political experience but a lot of charisma can glide down an escalator to win his party鈥檚 nomination and then the White House, there鈥檚 a sense that anything is possible. The Democratic Party establishment hasn鈥檛 decided what kind of nominee it should support in such an environment, the way it had with Mrs. Clinton four years ago. The media, burned from their 2016 coverage, are far more reluctant to label someone a front-runner too early.

And Democratic politics is shifting. The party鈥檚 base is to the left of where it was four years ago and is clamoring for diverse representation that comes from the bottom up. The small-dollar donor model that Senator Sanders embraced in 2016 is becoming less an exception than an expectation.

In this climate Mr. Biden, an older, white male candidate with a long history in politics and a聽less-than-stellar fundraising record, doesn鈥檛 seem quite as formidable.

鈥淚 don鈥檛 think he鈥檚 really as of the moment as [Sen. Elizabeth] Warren, Sanders, or the other candidates,鈥� says Jameson Hollis, a college student who came out to see Mr. Biden at a rally with striking Stop & Shop workers last week in the Dorchester neighborhood of Boston.

All that uncertainty makes it easier for more candidates to envision a path forward. And the growing number of contenders can of itself have an impact, by fracturing the electorate in the all-important Iowa caucuses and New Hampshire primary.聽If no one gets a majority 鈥� or even a convincing plurality 鈥� a dark horse candidate could easily remain in the game even after the polls close in those early states.聽聽

鈥淭he traditional metrics may not apply. And I say 鈥榤ay鈥� because the primaries are a political eternity away,鈥� says Democratic strategist Kelly Dietrich, founder of the National Democratic Training Committee, which prepares Democrats across the country to run for office but does not endorse specific candidates. 鈥淏ut the definition of what鈥檚 a hard red line where your chances are crushed are no longer the same.鈥�

鈥淣o one is getting scared out,鈥� he adds.

The new debate rules reflect this state of affairs. The Democratic National Committee wants to avoid appearing like it鈥檚 favoring higher-profile candidates over others. But it also wasn鈥檛 going to cram 20 people onto one stage. So now a lottery will determine which candidates will debate on Day 1 and Day 2. To qualify for the pool, a candidate only needs at least 1% support in three separate early-state or national polls, or have a minimum of 65,000 donors in 20 states, with 200 or more unique donors from each state.

鈥淚t鈥檚 very liberal criteria,鈥� says David Karol, a political scientist at the University of Maryland and co-author of 鈥淭he Party Decides,鈥� the 2008 book that codified the idea of the 鈥渋nvisible primary鈥� 鈥� the period of activity before the early primaries that used to essentially predetermine the party nominee.

鈥淎ndrew Yang is going to be in these debates,鈥� he says. 鈥淢arianne Williamson could be in these debates.鈥澛燤r. Yang is an entrepreneur-turned-philanthropist who joined the race in November 2017; Ms. Williamson an author and activist who declared in January.

Technology also plays a role, and not just because it鈥檚 revolutionized candidates鈥� ability to collect small donations from anyone, anywhere. Social media has made the process much more transparent. Much of what used to happen in back rooms between party leadership and prospective candidates 鈥� discussions about donor support and experience, and negotiations around what someone should run on and how 鈥� now takes place in the open for all the Twitterverse to see and comment on.

鈥淣ow there鈥檚 all these ways of measuring the candidates that are much more open and available,鈥� says Seth Masket, a politics professor at the University of Denver. 鈥淒o they actually have other people鈥檚 endorsements? Are they a good fundraiser? How well did they do in the last election?鈥�

Heightened transparency is a boon for lesser-known candidates like South Bend, Indiana, Mayor Pete Buttigieg, whose charisma makes him an easy fit for the social media era. 鈥淚n 1991 he just couldn鈥檛 have gotten to the place where he is, certainly [not] at this stage,鈥� Mr. Karol says.

It鈥檚 less helpful for Mr. Biden, whose long career 鈥� including a controversial role in Justice Clarence Thomas鈥檚 Supreme Court confirmation hearings, as well as a much-discussed reputation for handsiness 鈥� has lately come under scrutiny.

鈥淲hat鈥檚 loved about him is his experience,鈥� Mr. Masket says, but that also means he鈥檚 鈥渢aken stances that seemed like where the Democratic Party was in the 鈥�70s and 鈥�80s, but is not where it is today.鈥�

Still, the disapproval expressed by activists on Twitter isn鈥檛 necessarily shared by average voters.

鈥淲hen you鈥檙e a politician for that long, everybody is going to make mistakes,鈥� says聽Mike Linnane, a telephone worker from Boston, at the Stop & Shop rally. 鈥淗e鈥檚 for the middle class, and that鈥檚 what we need to bring back.鈥�

Many observers say it鈥檚 not time to throw out the rulebook 鈥� or Mr. Biden. The 2016 election was just one cycle, and it鈥檚 hard to know which lessons will most apply today. Social media and small-dollar donors certainly matter now, but big-name endorsements, polling, and debate performances will likely still be important too.

Will Mr. Biden give Democrats someone to coalesce around, as some pundits suspect? Or will the likes of Mr. Buttigieg and former Texas Rep. Beto O鈥橰ourke, with their viral viability, prevail? Perhaps primary voters will end up looking to California Sen. Kamala Harris, if she succeeds in walking the fine line between the party鈥檚 moderate and progressive wings.

Ultimately, it鈥檚 a question about the formula, not the ingredients.聽聽

鈥淎ll this stuff matters, and we don鈥檛 yet know which thing matters more,鈥� says Hans Noel, a Georgetown University professor who co-wrote 鈥淭he Party Decides.鈥� 鈥淲e鈥檙e still figuring it out.鈥�

Staff writer Clarence Leong contributed to this report.