Washington (CNN) Democrats got their first side-by-side view of the biggest names vying to lead the party -- and potentially its ticket against President Donald Trump in 2020.

More than a dozen senators, governors and House members got their first chance to flash their personalities, policy platforms and cases against Trump in front of a largely establishment audience at an "Ideas Conference" hosted by the liberal think tank Center for American Progress.

Here are five takeaways from the first potential candidate showcase of the 2020 election cycle:

The problem with focusing on Trump

Democrats sense that they're in the middle of a drop-everything moment, where nothing matters more to their voters than fighting Trump with everything they've got.

But those who want to lead the party in 2020 and beyond know they need to offer an optimistic and policy-focused message of their own, too.

The problem is, the transition from issuing dire warnings about the immediate emergency to selling a vision for a post-Trump America isn't a smooth one.

The messaging challenge facing Democrats was on display Tuesday. Most speakers simply attacked Trump at the outset of their remarks, and then -- with no real transition -- moved on to the policy topic they'd been assigned for the day.

Two senators seen as 2020 presidential prospects did try, though, to offer a cohesive vision.

New Jersey Sen. Cory Booker cast Trump as another of the "demagogues" -- Joseph McCarthy and Father Charles Coughlin were others he cited -- that have been obstacles to overcome in the arc of history.

"I want to fight in this climate. I want to dedicate myself," Booker said. "But we cannot just be a party of resistance -- we've got to be a party that's reaffirming the American dream."

Massachusetts Sen. Elizabeth Warren made a much more Trump-focused case.

She cast Trump's sharing of highly sensitive intelligence with Russian officials and his decision to fire FBI Director James Comey as symptoms of a political elite run amok.

"Concentrated money and concentrated power are corrupting our democracy and becoming dangerously worse with Donald Trump in the White House," she said.

The ideas on display here were broadly familiar. Many of the key talking points echoed the core principles that guided Hillary Clinton's campaign. They spoke soberly about technocratic solutions to all manner of economic displacement. Trump was dismissed as a craven bully.

"We can't allow Twitter wars to become shooting wars," former Obama national security adviser Susan Rice said to applause . Close your eyes, change a sentence here and there, and it could have been the late summer of 2016.

The touchier policy questions roiling the left in the Trump era were mostly glossed over. North Carolina Gov. Roy Cooper spoke with conviction, but the particulars -- "Investment in education has got to be all the way from birth through higher education" -- were gauzy and familiar. The repeated nods, over and again, to coal miners felt like clumsy lip service. (The whiplash came when Oregon Sen. Jeff Merkley suggested, to cheers, that the US "put every coal electricity generating plant into a museum by the year 2050.")

The 2020 anti-Trump messaging test drive

It's 42 months from Election Day 2020 -- but Democrats seen as presidential prospects used the first "cattle call" of the new cycle to take their best shots at Trump.

Sen. Kirsten Gillibrand focused on Monday night's report that Trump had shared classified information with Russian officials in the Oval Office last week. "Last night's reporting has taken us to a whole new level of abnormal. The President is truly creating chaos," she said.

For Warren, it was all economic inequality, all the time.

"The swamp is bigger, deeper, uglier and filled with more corrupt creatures than ever before in history," Warren said.

"The CEO of Exxon-Mobil is now the secretary of state. Goldman Sachs now has enough people in the White House to open a branch office," she said. "Do you get the feeling that if Bernie Madoff weren't in prison, that he'd be in charge of the SEC right now?"

Sen. Kamala Harris, a California freshman who many Democrats see as a rising star, harshly criticized Attorney General Jeff Sessions' push for harsher sentences for drug-related crimes -- and accused Trump and Sessions of "reviving the failed war on drugs."

Another Harris swipe at Trump carried racial, geographic and urban vs. rural implications. "We need this administration to understand that if they care about the opioid crisis in rural America as they say they do, they have also got to care about the drug-addicted young man in Chicago or East LA," she said.

The names you didn't hear

Specifically: Barack Obama, Joe Biden, Hillary Clinton and Bernie Sanders.

Tuesday's event was an opportunity for new Democratic leaders to take the stage without a former president or presidential candidate seizing the limelight. But it was impossible to ignore the shadow those figures still cast over their party.

Clinton's name rarely came up -- but occasionally, Democrats did take implicit shots at her 2016 campaign.

Minnesota Sen. Amy Klobuchar pointed out that Clinton's campaign did not pay attention to rural towns.

"Winning candidates do that," she said.

Montana Gov. Steve Bullock -- a two-time statewide winner in a place Trump cruised -- faulted the party for what he called an over-reliance on analytics and its focus on turning out the base.

Democrats should worry more, he said, "about really offering voters a reason to vote for a Democrat for president."

"From my perspective, Democrats need to do a better job of showing up, making an argument -- even in places where people are likely to disagree," he said.

Not all the cattle showed up for this 'call'

If this was Democrats' first semi-formal gathering of potential 2020 nominees, it was an incomplete one.

To the extent Tuesday's speakers were competing, it was to define their particular styles and cadences. The room was full of friends. When Virginia Gov. Terry McAuliffe, a longtime party fundraiser and Clinton super supporter, delivered his spirited argument about the importance of redistricting reform, his exaggerated drawl drew only warm smiles.

Warren, who probably tracks as far left as anyone of the keynote speakers, delivered the most round and polished remarks. Her decision to so vocally support Clinton in 2016 seems to have won her the trust of the party's liberal professional class.

But even as the politicians preached inclusion, it was, perhaps oddly, the panel titled, "The Resistance," that spoke in the harshest terms about the absent "cattle."

Daily Kos founder Markos Moulitsas dismissed "that grassroots Bernie (Sanders) thing" as a corrosive element that would forestall Democratic victories, even suggesting the Berniecrat call to win over working class whites was a cover -- "code," he called it -- for uglier ambitions.

"There's a changing of the guard in progressive leadership to one where women and marginalized communities are centered. It doesn't mean they're part of the party anymore, they're leading it. And there is some resistance among some corners of that, and you see it in things like people saying, 'Well we need to reach out to working class people,'" Moulitsos said. "Because, you know, none of us know any working class people in our communities."

Sanders was not present because CAP, as a spokeswoman explained, did not offer invitations to anyone who had previously run for president.

Still, the absence of anyone -- Warren aside -- who might feasibly win his and his supporters' enthusiastic support gave the event a narrower feeling.

Few new ideas on health care

Democrats here were prepared to fight and die in defense of Obamacare. Activists and organizers onstage and off pointed to the Republican bill as the party's ticket back to a House majority.

The language was stark. House Minority Leader Nancy Pelosi called the Republican bill "deadly" and "the most damaging bill for women in legislative history."

Of all the issues coming down the pike, health care is "the huge one," Indivisible Project co-founder Leah Greenberg told CNN before her panel discussion.

And still, the elephant in the room went unaddressed. Through a full day of speeches, group discussions, and one-on-one chats, the question of what, specifically, Democrats would pursue and sell voters -- beyond preserving and beefing up the ACA -- went unanswered.

Single-payer health care, or "Medicare-for-all," a demand of the progressive left movement led by Sanders, never came up. No one for, no one against -- though by its absence, the message was clear. Democrats in Washington, and those who perhaps aspire to careers in the city, are still choosing caution.

Adam Green, co-founder of the Progressive Change Campaign Committee, praised Warren for her "big ideas" on job creation, and shouted out Los Angeles Mayor Eric Garcetti and Oregon Sen. Jeff Merkley for their ambitious infrastructure programs.

But he conceded that health care would be a tougher nut to crack.

"It will take discipline," he said, "for progressives to pivot to offense and use the oxygen in the room to educate Americans about Medicare for All and big-picture themes like taking on the insurance industry monopolies."

There is still more than a year until the midterm elections, and maybe a little while longer before big decisions are made ahead of the party's presidential primary, but the health care divide isn't going away.

And like any other fight among mostly like-minded people, the longer it lingers, the nastier the eventual reckoning.