Cedar Rapids, Iowa (CNN) Nearly every Democrat vying to take on President Donald Trump in 2020 made their pitch to Iowa's most plugged-in Democrats on Sunday, looking to set themselves apart from the sprawling field of candidates in the midst of a swirling carnival of activists and campaign volunteers.

The event brought together four of the five top candidates in CNN's newly released poll , which found a tight race forming in the Hawkeye State, with former Vice President Joe Biden -- who was not present on Sunday -- holding onto a lead, with Sens. Bernie Sanders and Elizabeth Warren trailing him and South Bend Mayor Pete Buttigieg on their tails.

With 19 speakers allowed just five minutes, each candidate sought to break out before the activist crowd here in East Central Iowa -- usually by hitting Trump in a new or creative way, knocking their Democratic opponents or casting themselves as an entirely different choice.

Bash Biden, berate Trump, or both?

Despite Biden's frontrunner status, most of the candidates refused to go directly after the former vice president, who attended his granddaughter's graduation ceremony instead and will visit Iowa later this week.

Instead, it was Trump who drew most of the ire.

"He claims to be the best president we have seen in a generation. Well, I say let's call Barack Obama, because that's identity fraud," California Sen. Kamala Harris said.

Former Colorado Gov. Jay Hickenlooper called Trump "the worst president in the history of America." Vermont Sen. Bernie Sanders said Trump is "a liar, a racist, a sexist, a homophobe, a xenophobe, a religious bigot, and someone who believes that he is above the law."

The candidates who sought to offer a sharper contrast with their primary rivals either targeted Biden -- or at least his style of politics -- or, from the other side, Sanders and his Medicare for All plans.

Buttigieg said Democrats will not win in 2020 by "playing it safe, of promising a return to normal."

"We are where we are because normal broke," Buttigieg said, arguing that Democrats cannot promise normalcy or going back to the 1990s or 2000s, a line the mayor has worked into recent speeches as a subtle knock on Biden.

Much like he did at the California state convention last week, Sanders in his speech warned that entering 2020 with "middle ground" positions risks dulling the argument against Trump and the wider Republican agenda.

"I understand that there are some well-intentioned Democrats and candidates who believe that the best way forward is a middle ground strategy that antagonizes no one, that stands out to nobody and that changes nothing," Sanders said, again making the implicit argument against Biden. "In my view, that approach is not just bad public policy, but it is a failed political strategy that I feel could end up with the reelection of Donald Trump."

But Sanders has his critics -- and they used their platforms to pushback against his agenda and question his electability.

Former Maryland Rep. John Delaney, a critic of Medicare for All, ticked off a list of European countries -- "whose systems we admire" -- that guarantee universal health care using models that keep a role for private insurers, which Medicare for All, in almost every case, does not.

Hickenlooper argued that Sanders would be an easy mark for Republicans.

"We must present a bold vision for the future," Hickenlooper said, "but we also must acknowledge that the most effective attack the Republicans can level against us is 'socialism.'"

The day-long affair -- which included some campaign staffers waking up at 4 a.m., to position themselves and boisterous supporters lining the streets with thousands of signs and eye-grabbing spectacles -- represents the informal kickoff of the Iowa caucus season, with each campaign hoping to use the speech as a springboard to a summer full of organizing.

But for many, the event was just about getting some attention -- from the media and activists.

"The challenge is that people just don't know my name," said Washington Gov. Jay Inslee. "That's the principal challenge."

And the historic size of the Democratic field impacted the event in a number of unique ways.

It was difficult to move a few feet in the Cedar Rapids' venue without bumping into a candidate for president, a situation that created some unique interactions between competitors and their supporters. Sanders walked into the venue before the event as Harris supporters chanted about electing a woman to the White House, Hickenlooper and the California senator shared cheddar popcorn before both went on stage, and a bagpiper -- paid for by Delaney -- blared in the middle of Minnesota Sen. Amy Klobuchar's speech rallying her supporters outside the venue.

Each candidate was given five minutes of time on stage, with those who ran long being played off by loud Oscars-style music. The short time also forced speakers to make impressions off the stage, so the candidates mingled, chanted and rallied with their most ardent supporters outside the venue. Candidates and their spouses ran into each other. Activists chanted, cheered and marched through the streets.

The spectacle outside

Sanders led a "Fight for 15" solidarity march with striking McDonald's workers demanding a $15-an-hour minimum wage and a union, filling the street in front of the venue after headlining a rally nearby a few minutes earlier.

Former Texas Rep. Beto O'Rourke's campaign brought in a Moys breakfast taco truck and handed out flyers that offered a free taco to other campaigns' volunteers "in appreciation of your support for the many Democrats running 4 POTUS." Later, his campaign bought a long table full of Casey's Pizza for those leaving the event.

Delaney's team included at least a pair of sign-spinners and a helium-filled mini-blimp displaying the former Maryland congressman's name.

New Jersey Sen. Cory Booker made perhaps the largest organizing push, with chants and cheers echoing through the venue as his supporters followed him in.

And Buttigieg's campaign hosted a sprawling picnic that included bag toss, food truck and live music, with the mayor himself playing the keyboard before marching over to the event flanked by his supporters.

Outside groups were also on hand. Volunteers with the Sunrise Movement and other environmental organizations pushed candidates to address climate change. A Greenpeace scoreboard rating 2020 Democrats was on display across the street from the dinner. Supporters of The Young Turks chanted "sign the pledge," urging Democrats to promise their support for a progressive economic platform the left-leaning news outlet recently unveiled.

Iowa Democrats celebrated two freshman congresswomen, Abby Finkenauer and Cindy Axne, who both won office in a midterm election in which female candidates and voters fueled the Democratic surge to a House majority.

New York Sen. Kirsten Gillibrand seized on that fact, making a direct appeal to the women in the room "and the men who love them" by urging Democrats to see the fact that women led Democrats back to control of the House in 2018 that a woman can win in 2020.

"Women are on fire in America today. We have marched, we have organized, we have run for office and we have won. Because of women we flipped the US House of Representative," she said, imploring the crowd to believe "now is not the time to be polite, now is not the time for small steps, now is the time to fight like hell."

Struggling for attention

Gillibrand has struggled to get traction in a field where only five candidates are polling above 5% in Iowa. Female candidates who are well-known in Washington, like Gillibrand and Klobuchar, are fighting for oxygen in a field with two older white men in Biden and Sanders leading.

"Every so often I get sad about the numbers for some of the women -- including everyone, our combined numbers and what they are -- but I think it has been improving and I think people are taking us seriously and I think the debates are going to be a really good chance for the woman to show their stuff," Klobuchar said Saturday while campaigning in Cresco.

"Could we be running with less experience than we had?" she asked about the men in the race. "I don't think so. I don't think people would take us seriously."

At such a crammed and fast-paced event, lesser-known candidates fought just to put themselves on Iowa Democrats' radars.

Montana Gov. Steve Bullock accused Trump of turning elections into "dark money auctions" and touted his legal fights against the Koch brothers.

Colorado Sen. Michael Bennet railed against Senate Majority Leader Mitch McConnell, the Kentucky Republican.

"Trump is the star of his own three-ring circus in Washington, but there is no doubt who the ringmaster actually is," he said.

Hawaii Rep. Tulsi Gabbard pledged to end "wasteful regime change wars that have taken so many lives." California Rep. Eric Swalwell promised to "be bold, without the bull."

Inslee said he wants to oppose Trump with his experience as the leader of the state with "the single best economy in the United States."

"That's going to drive him nuts," Inslee said.