A lot has changed since Sen. Bernie Sanders' first bid for president, but perhaps the biggest change is the structure of the primaries themselves.
Sanders is now well-known, considered to be a front-runner in the 2020 race, and he's demonstrated the ability to raise huge amounts of money using small donations. But a notable change for Sanders from 2016 has to do with the primary schedule.
Instead of holding their primaries in the spring, California and Texas are among a number of states that will be part of Super Tuesday in the beginning of March 2020.
During the 2016 campaign, it was important for Sanders to show early strength as a candidate. That's why he spent a lot of time in Iowa and New Hampshire.
The early work paid off: Sanders almost defeated former Secretary of State Hillary Clinton in the Iowa caucuses, and he won big in New Hampshire. Then the campaign was forced to quickly throw together organizations in many states across the country.
This year is different. Sanders adviser Josh Orton said the campaign is in the process of putting together strong organizations in dozens of states right from the start.
"The campaign will be getting involved and building volunteer lists and building the infrastructure not just in the first couple states but we have to look past the first couple states ... It's essential that in this election cycle, in this primary, that candidates are able to sort of walk and chew gum at the same time."
Norwich University political science professor Ted Kohn thinks the major change in the primary schedule could have a significant impact on this race.
"I think it's a pretty big game changer,” said Kohn. “I think especially in a crowded field this might very well make people stay in the race longer than simply after the first round of the four corner states of Iowa, New Hampshire, South Carolina and Nevada."
Kohn expects that Sanders will do well again in Iowa and New Hampshire. He said an early test for the campaign will come in the next two states: South Carolina and Nevada. These are states where Clinton defeated Sanders in 2016.
"But I think it's these other states as well that are going to prove, you know, is he really the national phenomenon that he was in 2016?” said Kohn.
UVM political science professor Ellen Andersen thinks it's essential for Sanders to sweep the first four states if he's going to have a solid chance to win the nomination.
"He doesn't have to win California — he just needs not to lose California too badly — but he more or less has to take the other states,” said Andersen.
The new primary campaign calendar also poses some strategic questions for the candidates.
Former Middlebury College political science professor Eric Davis said Sanders and the other Democratic candidates will have to weigh the pros and cons of finishing first in a small state with just a few delegates versus a competitive finish in a much larger state.
“You can come in first in the New Hampshire primary, but end up with a very small number of delegates which would be much less than you would get from finishing say second, rather than third, in California,” said Davis.
Another key issue to consider in the 2020 race, Davis said, is that delegates are awarded on a proportional basis depending how the candidates finish — but there's a 15 percent threshold to win any delegates.
For instance, in the Vermont primary in 2016, Hillary Clinton received almost 14 percent of the vote but didn't meet the threshold, so she was awarded no delegates based the vote.
It wasn't a major concern in 2016 because the field of candidates was so small, but now it could emerge as a significant factor with potentially more than 20 candidates in the race.
Davis said this could rule could have a huge impact on how delegates are awarded in 2020.
"You could come up with a hypothetical scenario where a candidate could win say, half the delegates in California with only 30 percent of the vote, but coming in as the plurality winner getting more votes than anybody else," he said.
Another change this year involves so-called superdelegates, a group of longtime party leaders who were appointed — not elected — as delegates.
Four years ago they represented about 15 percent of all Democratic delegates. That emerged as a big problem for Sanders because more than 90 percent of them announced their support for Clinton early in the campaign, giving her a sizeable lead over Sanders at the outset of the race.
Sanders was very critical of this process saying it was a highly "undemocratic" way to select delegates, and he successfully worked to limit their role in 2020. Now superdelegates will be allowed to vote only if no candidate wins the nomination on the first ballot — a change designed to give primary voters more power.
Sanders is currently on a three-day trip to Iowa and he's scheduled to hold a campaign rally in Concord, New Hampshire, on Sunday.