HOUSTON — Democrats argued over topics from health care to race to gun laws, and one even promised to give away free money during a sprawling three-hour debate Thursday that brought the party’s 10 leading presidential candidates onto the same stage for the first time.

The event put all three leading candidates, Joe Biden, Bernie Sanders, and Elizabeth Warren, in the spotlight at once, and came just over four months before the first votes will be cast in the Iowa caucuses.

Unlike past debates, there was no singular moment. Here are some of the takeaways from the evening, plot lines likely to play out in coming weeks on the campaign trail:

Biden makes a claim to ‘bold’ action, challenges Warren, Sanders

Biden had been a target during each of the first two Democratic debates, as rivals attacked him as too incremental in his approach, not bold enough. The former vice president sought to counter both from the very start Thursday night in what, for much of the debate, was his most energetic performance so far.

He painted his ideas as big and ambitious, tying them to John F. Kennedy’s call to go to the moon.

“I refuse to postpone for one more minute spending billions of dollars on curing the cancer, Alzheimer’s, and other diseases,” Biden said in his opening statement, quoting Kennedy and later touting a “bold” plan to increase funding for schools in low-income areas.

At the same time, he went in the other direction by arguing that Medicare for All, single-payer health-care plans backed by Sanders and Warren, would be too unwieldy and costly. “How are we going to pay for it?” he challenged during the first answer of the night.

Warren, appearing on stage with Biden for the first time, did not directly engage with him. Instead, she defended Medicare for All by arguing that even if taxes rise, people will pay less overall in taxes and health costs.

“Families are paying for their health care today," she said. "Families pay every time an insurance company says, ‘Sorry, you can’t see that specialist.' Every time an insurance company says, 'Sorry, that doctor is out of network.’ ”

It was a sign of things to come: Warren largely passed on directly challenging Biden, and was quiet for long stretches of the debate, despite entering the night as one of the candidates riding the most momentum.

Meanwhile, Sanders, edging down in some polls, directly confronted Biden.

“We are spending twice as much per capita on health care as Canadians,” Sanders said, to which Biden shot back: “This is America.”

“Yeah," Sanders said, “but Americans don’t want to pay twice as much as other countries.”

Warren and Sanders put on the defensive on Medicare for All

Health care has become the key issue for Democrats, but Thursday’s debate offered a clear dividing line for Warren and Sanders, who support a plan with no private option, and the others.

This time, though, Biden was joined by Minnesota Sen. Amy Klobuchar, South Bend, Ind., Mayor Pete Buttigieg, and California Sen. Kamala Harris in pushing against an entirely public plan.

“The problem with that damn bill you wrote and that Sen. Warren backs is that it doesn’t trust the American people,” Buttigieg said. “I trust you to choose what makes the most sense for you.”

Biden challenged Warren and Sanders to better explain how their plans would be paid for, arguing the cost was unrealistic.

“I know the senator says she’s for Bernie,” Biden said of Warren. “I’m for Barack.”

That was a common refrain of all the candidates — complimenting President Obama’s Affordable Care Act before delving into how they would tweak, or replace, it.

Looking for oxygen, Castro jabs at Biden, Yang says he’ll give out money

Some of the candidates in the lower tier of candidates tried to make waves, because they might not get many more chances to change a race remarkable for its stability.

Former HUD Secretary Julian Castro said Biden’s health-care plan would leave 10 million Americans uninsured and would require them to buy in to the plan.

“Are you forgetting already what you said two minutes ago?” Castro asked, speaking over Biden and repeatedly, asking him if he forgot, in a not-so-subtle jab at Biden’s age.

The exchange prompted applause and jeers from the crowd. Buttigieg interjected, “This is why presidential debates are becoming unwatchable.”

Entrepreneur Andrew Yang started the night off by announcing he’d give $1,000 a month to 10 randomly chosen families, as a demonstration of his signature plan for a universal basic income. He had teased the announcement on social media ahead of the debate. Some election-law experts, though, quickly questioned the legality of the plan.

Focus on race, but not reparations

With Democrats depending heavily on black and Hispanic voters as a major part of their coalition, the debate devoted significant time to questions of racism, inequality, and President Donald Trump’s role in fueling prejudice. But this time the candidates mostly steered clear of talk about reparations, an idea that has polled badly and worried some Democrats that their party was hurting itself in the general election.

Instead, the candidates offered a number of seemingly less controversial ideas. New Jersey Sen. Cory Booker pledged to create a White House office to focus on combating white supremacy, and touted ideas such as further reforms to criminal sentencing, and addressing disparities in health care and “environmental injustice in communities of color all around us.”

Harris pledged to increase funding for historically black colleges and universities. Former Texas Rep. Beto O’Rourke pointed to disparities in how children of color are disciplined in school compared with white kids and disparities in the health-care system.

In each case, they touched on ideas that could have tangible impacts but with less divisive political implications.

O’Rourke has a moment on gun control

Many of the candidates blamed Trump’s rhetoric for the El Paso shooting, no one stronger than O’Rourke, who suspended his campaign to go to his hometown after the massacre there.

O’Rourke said he would institute a mandatory buyback of assault weapons.

“Hell yes, we’re going to take your AR-15 and your AK-47," he said. "We’re not going to let it be used against our fellow Americans anymore.”

Harris said that while Trump didn’t pull the trigger in El Paso, “he’s certainly been tweeting the ammunition.” On the whole, there was outrage and bold ideas but few answers on how to pass gun control through Republicans in Congress.

Klobuchar said that Democrats should focus on current, more incremental legislation. “We can’t wait until one of us gets into the White House," she said.

Warren said the solution lies in getting rid of the filibuster

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Will it matter?

If there’s anything the first two debates showed, it’s that the instant analyses are often way off base.

Harris, Booker, and Castro were widely declared to be the big performers in the first two debates, while Biden was slammed as lethargic. Yet aside from a short-lived polling bump for Harris (which she then lost), none of those supposed “winners” gained much ground, and the most constant part of the race is that Biden has stayed at the top of the field, according to polls.

So whatever the initial impressions, experience says we’ll have to wait some time to have a real sense of whether anything that happened in Houston will significantly change what has been a stable race for months.