With four nominating contests down, 155 pledged delegates have now been divided among the Democratic presidential candidates.
But this Tuesday — Super Tuesday — the stakes get a lot higher.
More than 1,300 delegates, about one-third of the available total, will be in play as 15 states and territories and Democrats abroad vote.
Their departures were seen as a way of clearing the path for Mr. Biden, but it pays to remember that voters’ candidate choices are not always driven by policy affinity. So it is not clear that any one candidate will benefit.
Mr. Biden faces several big obstacles on Tuesday. First, in most states his campaign has lagged in ground operations and TV spending. Second, Michael R. Bloomberg — the billionaire and former New York mayor, who most certainly does not have a resources problem — will compete for the first time, appearing on the ballot in all Super Tuesday states.
Besides that, Senator Bernie Sanders of Vermont, the front-runner, is well positioned in many of the states that will vote on Tuesday, including California and Texas. A few decisive victories could make his path to the nomination much clearer, although it might still be hard for him to accrue an outright majority of delegates before the convention.
Senator Elizabeth Warren of Massachusetts has at least one bright opportunity in her home state, though Mr. Sanders is threatening to spoil the party there. She could also pick up delegates in other crucial states, even if she falls short of winning the states themselves.
Here is a look at what polls are telling us about the six states with the most delegates on the Super Tuesday map.
California: 415 pledged delegates
The big prize. California moved its primary up to Super Tuesday for 2020, and its enormous delegate haul makes this newcomer the instant star. With its relatively liberal, heavily Latino Democratic electorate, it is well suited to Mr. Sanders. And sure enough, he holds a commanding lead in most California polls, including a CNN poll published on Friday that put him more than 20 points ahead of his closest rival.
If those numbers hold, all of his opponents will be at risk of falling short of the 15 percent threshold needed to claim any statewide delegates, though they could still win delegates in congressional districts.
Ms. Warren is in contention for second place in many polls. As long as she hits the threshold, she could pick up a sizable chunk of delegates without winning the state. Mr. Biden and Mr. Bloomberg are also within striking distance.
Texas: 228 pledged delegates
With Super Tuesday just three days after the South Carolina primary, there simply isn’t much polling available to tell us how much wind that victory has put in Mr. Biden’s sails.
Texas is Exhibit A for all that uncertainty. Mr. Biden and Mr. Sanders had been running neck-and-neck there since January, but recent polls have shown Mr. Sanders pulling ahead. His well-funded campaign has invested heavily in the Lone Star State, seeking in particular to drive turnout among its large Latino population, which made up roughly one-third of the Texas Democratic primary vote in 2016, according to exit polls.
An NBC News/Marist College poll released Sunday showed him leading Mr. Biden by 15 points, with Mr. Bloomberg in third place.
Mr. Sanders also has a formidable opponent on the left in Ms. Warren, who grew up in neighboring Oklahoma and taught at universities in Houston and Austin. She landed at 15 percent in a CNN poll of Texas released Friday. (She was at 10 percent in the NBC/Marist poll.)
Mr. Bloomberg’s money is also a factor: He has flooded the airwaves in Texas, placing 80 percent of all political ads in the state, according to an analysis by The Dallas Morning News.
North Carolina: 110 pledged delegates
Next door to South Carolina, the Tar Heel state long seemed like an almost equally safe bet for Mr. Biden. But early this year, as Mr. Bloomberg’s campaign accelerated and Mr. Sanders consolidated his support among liberal voters (a more plentiful group here than in South Carolina), Mr. Biden dropped in the polls.
All three of those candidates stand a good chance on Tuesday. A recent University of Massachusetts Lowell poll conducted by YouGov showed Mr. Sanders edging ahead with 23 percent support, Mr. Bloomberg at 19 percent and Mr. Biden at 16 percent. But an NBC/Marist poll of North Carolina, also released Sunday, found Mr. Sanders (26 percent) and Mr. Biden (24 percent) in a statistical dead heat, while Mr. Bloomberg came in third at 15 percent.
In that NBC/Marist poll, Mr. Biden led Mr. Sanders by just 12 points among black voters. But polls in South Carolina consistently underestimated his African-American support. If he can get closer to his margin in South Carolina — where he beat Mr. Sanders by more than three to one among black voters, according to exit polls — he could run away with North Carolina.
Virginia: 99 pledged delegates
With a highly educated, heavily suburban Democratic electorate, Virginia may offer Mr. Bloomberg his best shot at a significant victory on Tuesday. A Monmouth University poll last month showed Mr. Sanders and Mr. Bloomberg tied at 22 percent, with Mr. Biden at 18 percent — technically a three-way statistical tie.
In that poll, Mr. Biden maintained a two-to-one lead over both Mr. Bloomberg and Mr. Sanders among black voters, but he significantly trailed each of them among voters making less than $100,000 a year, a demographic that has been crucial for both him and Mr. Sanders.
Massachusetts: 91 pledged delegates
A WBUR poll out Friday found Mr. Sanders jumping out to an eight-point lead, but a Boston Globe/Suffolk University survey released a day later showed a tighter race, with him at 24 percent and Ms. Warren at 22 percent.
Ms. Warren also got a boost last week when The Globe endorsed her.
She affirmed last week that she planned to stay in the race if Mr. Sanders fell short of a delegate majority, and she has shown a sustained ability to fund-raise that could keep her in the running through the summer. So, in the event of a contested convention, she may seek to present herself as a consensus choice. By that logic, a victory on Tuesday in at least one state could be crucial to establishing her credibility as a candidate who can win.
Minnesota: 75 pledged delegates
Until Monday, the story seemed to be similar in Minnesota, where Ms. Klobuchar was out front in her home state with 29 percent of the vote in a Star Tribune/MPR News poll. But she has now decided to throw her support behind Mr. Biden.
It is unclear what that will mean for the state, where her popularity was so great that none of her moderate rivals — Mr. Biden, Mr. Buttigieg or Mr. Bloomberg — got more than 8 percent in the Tribune/MPR poll. Mr. Sanders, who enjoyed one of his most resounding victories of the 2016 primary campaign in Minnesota, ran a strong second at 23 percent in that survey.
Will enough of Ms. Klobuchar’s supporters coalesce behind Mr. Biden? Or will her departure clear the way for Mr. Sanders to rack up another big win? Another possibility: A sizable number of her supporters could jump to Ms. Warren — the only candidate other than Ms. Klobuchar and Mr. Sanders to reach double digits in the Tribune/MPR poll.