DES MOINES – The leading Democratic White House contenders drew stark contrasts with each other Friday night at the largest gathering of party activists before one of them accepts the party's presidential nomination next summer in Milwaukee.

The event marked the beginning of a frenzied three-month sprint to the Iowa caucuses, when voters will meet in school cafeterias and community centers around the Hawkeye State to kick off the party's nominating contest.

While the candidates did not name each other in their speeches, they openly feuded over expansive plans to overhaul the American health care system, address a rising volume of student debt and heal the deep partisan schisms that have split the nation.

For a party badly shaken by Trump's unexpected election in 2016, the subtext for many emerging battle lines in the Democratic race is the ability to take on Trump in a nationally televised debate – and in the midst of what is likely to be a multi-billion dollar fight for the White House.

Biden, trying to arrest his slide in the polls, cast himself as the most electable candidate in the crowded Democratic field, with his fans rattling together thunder sticks to echo his pledge to beat Trump "like a drum."

"We can make sure that the 160 million people who have private insurance can keep it if they want," Biden said. "There will be no tax increases on the middle class. None, none, none."

Despite the attacks, several Warren advisors said privately they were pleased that her decision to release details of the plan earlier Friday was driving the conversation.

Warren said the ambitious and costly plans she has rolled out are aimed at inspiring the voters Democrats will need to reclaim the White House.

"And here's the critical part: We need to be willing to fight for them. It's easy to give up on a big idea. But when we give up on big ideas, we give up on the people whose lives would be touched by those ideas."

Both Warren and Buttigieg have clashed over the contours of the campaigns they hope to mount against Trump. Warren has emphasized her willingness to fight and Buttigieg appeals with a promise to bring a divided nation together. They each cast the other's outlook as naive.

"I didn't just come here to end the era of Donald Trump. I am here to launch the era that must come next. Because in order to win and in order to lead it's going to take a lot more than the political warfare that we have come to accept from Washington, D.C.," Buttigieg said Friday.

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"I will not waver from my commitment to our values or back down from the boldness of our ideas, but I also will not tire from the effort to include everyone in this future we are trying to build. Progressives, moderates and Republicans of conscience who are ready for a change," he said. "I will never allow us to get so wrapped up in the fight that we start to think the fighting is the point. The point is what's on the other side of the fight."

Half an hour later, Warren seemingly addressed Buttigieg directly.

"Anyone who comes on this stage and doesn't understand that we are already in a fight is not the person who is going to win that fight. Anyone who comes on this stage and tells you they can make change without a fight is not going to win that fight. And anyone who comes on this stage and tells you to dream small and give up early is not going to lead our party to victory," she said.

"They think that running some vague campaign that nibbles around the edges is somehow safe. But if the most we can promise is business as usual after Donald Trump, then Democrats will lose. We win when we offer solutions big enough to touch the problems that are in people's lives. Fear and complacency does not win elections. Hope and courage wins elections," Warren said.

Harris, who laid off staff this week amid fundraising struggles, delivered a strong address Friday, casting herself as a fighter for justice in an increasingly unjust world. Along the way, and in front of perhaps the biggest crowd of supporters that any campaign attracted to the rafters of the Wells Fargo Center, Harris managed to land blows against virtually every one of her leading rivals.

"To win, it can't be about anything other than looking at the future. It can't be about looking at yesterday, we need to be focused on tomorrow," Harris said, an apparent reference to Biden's promise of returning to an earlier and possibly mythical era of civility in politics.

Days after a New York Times report that Warren defended some corporations in court, Harris – a former district attorney and California attorney general – drew a distinction with her Senate colleague.

"I've only had one client in my life, and that's the people," Harris said. "Unlike others, I've never represented a corporation. I've never represented a special interest."

Klobuchar ended as perhaps the unluckiest candidate of the night. In need of another strong performance to build her momentum, Klobuchar pulled a late slot, speaking after many of the party activists who applauded enthusiastically at the beginning of the night had filed out.

Even in front of a diminished crowd, Klobuchar, the Midwestern moderate, took a stab at Warren's Medicare for All plan.

"I will have plans that I can pay for and deadlines that I can meet that are grounded in reality," she said.

As more Iowa Democrats begin to pay attention to the candidates fanning out across the state this weekend, presidential contenders are under increasing pressure to show momentum and growth.

"I am running for president because like so many of you in this room I am a parent and a patriot. I have seen the future that lies ahead for our children and it is not something I am willing to accept," Yang said.

The Iowa Democratic Party declined to say how many tickets each campaign had purchased, but Buttigieg, the Millennial mayor of the 306th-largest city in America, had what appeared to be a thousand or more supporters to shriek gleefully from three tiers of seats.

"I don't have to throw military a military parade just to see what a convoy looks like," said Buttigieg, a veteran of the war in Afghanistan.

None of the candidates on Friday matched Obama's rhetorical gifts, though a few – most notably Buttigieg, who spoke of campaigning in Iowa on behalf of another candidate with a funny name – clearly tried.

At least one candidate vying for increasingly rare oxygen in a crowded field showed some self deprecating awareness.