Brianne Pfannenstiel | The Des Moines Register

Nineteen presidential candidates, 1,500 Democratic activists and about 100 members of the media will descend on a Cedar Rapids ballroom Sunday in what will be the largest event of the 2020 Iowa caucus cycle so far.

Although candidates have already held more than 400 events in Iowa this year, the Iowa Democratic Party Hall of Fame event marks the start of the summer caucus season, when candidates swarm the state at an even faster pace to make their cases to potential supporters. The multi-candidate gathering is an early test of their organizational prowess and an opportunity to break out from the massive pack.

"This is the first time to see a majority of them toe-to-toe," said Linn County Democratic Party Chairman Bret Nilles. "Four years ago, that was Hillary Clinton, Bernie Sanders, Martin O’Malley, Lincoln Chaffee and Jim Webb. Right away, you could start to see who those top-tier candidates are and who’s going to start surfacing to the top — you can always feel that in the room when someone’s speaking. Who’s the one that really has turned it up a little and appeals to the audience?"

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Here's a look at what to watch during Sunday's Hall of Fame event:

Who's in the room

The Grand Ballroom at the DoubleTree Hilton in Cedar Rapids will be filled to capacity. But it isn’t a free and open-to-the-public event.

Tickets to get in were offered equally to each of the active campaigns. The campaigns could decide whether and how many tickets to purchase, said Mandy McClure, communications director for the Iowa Democratic Party. After the campaigns claimed their tickets, the rest went on sale to the general public. Those tickets cost from $75 for general admission to $10,000 for a VIP table.

Look for those candidates who are well-funded and well-organized to fill their tables.

The candidates currently scheduled to speak are Colorado Sen. Michael Bennet, New Jersey Sen. Cory Booker, Montana Gov. Steve Bullock, South Bend, Indiana, Mayor Pete Buttigieg, New York City Mayor Bill de Blasio, former Maryland U.S. Rep. John Delaney, Hawaii U.S. Rep. Tulsi Gabbard, New York Sen. Kirsten Gillibrand, California Sen. Kamala Harris, former Colorado Gov. John Hickenlooper, Washington Gov. Jay Inslee, Minnesota Sen. Amy Klobuchar, former Texas U.S. Rep. Beto O'Rourke, Ohio U.S. Rep. Tim Ryan, Vermont Sen. Bernie Sanders, California U.S. Rep. Eric Swalwell, Massachusetts Sen. Elizabeth Warren, author and entrepreneur Marianne Williamson and businessman Andrew Yang.

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Who's flexing their organizing muscles

Multi-candidate “cattle calls” like the Hall of Fame dinner create a platform for campaigns to showcase their organizational strength. Look for campaigns to put together boisterous displays of support both before and after the event.

Harris and Booker have organized rallies for their supporters on site before the program is set to begin. Buttigieg will host a picnic for his supporters, and Warren will have volunteers lining the route into the convention hall with signs and other shows of support.

“I do think it’s going to be a pretty big show,” McClure said.

In the ballroom, look for campaigns to know which are their candidate’s go-to applause lines and listen for them to make noise accordingly.

“This is an organizing exercise,” said Des Moines attorney and former Democratic operative Grant Woodard, who is not aligned with a 2020 candidate. “I think it’ll probably be pretty clear who has campaign staff and who does not. … I think it’s going to start setting up some of the dividing lines in this race of who really has the resources to compete here.”

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Who's not in the room

One person will be conspicuously absent Sunday: Former vice president and current frontrunner Joe Biden declined the party’s invitation. He is the only high-profile presidential candidate to skip the event.

“I don’t think being there or not is going to make or break his candidacy,” said Linn County's Nilles.

But Biden does risk rankling party activists, who worry about candidates taking the state for granted. That was the case last week when he skipped the California Democratic Convention, which drew 14 other candidates.

There, Sanders leaned into that resentment and subtly criticized Biden (although he didn't name him) for skipping the event. Will he do the same in Iowa? Sanders most closely follows Biden in national and state polling.

Instead of wading into the fray at the dinner, Biden plans to return to Iowa on Tuesday, June 11, to campaign on his own terms.

The former vice president so far has embraced his frontrunner status, choosing to draw contrasts with Republican President Donald Trump rather than his Democratic challengers. Those contrasts will be sharp in Iowa next week: Both Trump and Biden will be in the state on the same day.

So far, Trump has reserved most of his attention for Biden, whom he seems to have identified as his greatest threat. Can anyone else provoke Trump into responding to something they've said when he's in the state?

► Keep up to date with all of the candidates' Iowa campaign events by bookmarking our 2020 candidate tracker.

Who can break out of the pack

Each of the candidates will have only five minutes on stage to make their case, land a punch or make a headline.

Some of the polling leaders may be able to play it safe and fall back on a shorter version of their standard stump speech. But some of the lesser-known candidates have to find a way to start standing out in a crowded field, Woodard said.

"You really need to look for some sort of major moment in which you can separate yourself from the pack and show why you’re in this race," he said. "I know it’s still June and it's six, seven months from the caucuses, but these opportunities are quickly dwindling."

McClure said that, as of Monday, close to 100 members of the media had signed up to cover the event. For lesser-known candidates in the 24-candidate field, the attention presents a massive opportunity for breakout and viral moments.

Candidates — particularly those who need a boost to make the debate stage later this month — could take bolder approaches to their speeches. The cutoff for candidates to meet the donor and polling thresholds is Wednesday, June 12, and the Democratic National Committee just recently announced an even higher threshold to make debates in September and October.

“I think you’re going to see more campaigns … trying to really make a splash or make a haymaker versus someone that they perceive as being in their lane,” Woodard said. “You see this at any election near cutoff time: People get more desperate; they get a little more blatant or open with their attempts at it.”

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Will anyone start to draw sharper distinctions

So far, the candidates who have gone on the attack have focused their attention on Biden.

Although it's been subtle, Sanders, Warren and Buttigieg have recently sought to draw distinctions between themselves and the former vice president. Will they continue that in Cedar Rapids, or will anyone seek to show sharper separations within the broader field?

This is the first Iowa event that will host Sanders and Warren, two of the most progressive candidates, on the same stage. Will they work to draw contrasts with each other?

Other, more moderate Democrats have sought to stand out by distancing themselves from some of the party's more progressive policy proposals, such as "Medicare for All."