Ten Democrats clashed in the first debate of the 2020 presidential race Wednesday with Elizabeth Warren cementing her status as a top-tier candidate and several underdogs using the issue of immigration to clamor for the limelight.

The biggest American political debate since the 2016 presidential campaign is occurring over two nights in Miami, climaxing Thursday with former vice president Joe Biden squaring off against nine challengers, including number two candidate Bernie Sanders.

But Wednesday's first take was a spirited encounter between Democrats like ex-congressman Beto O'Rourke, Senator Cory Booker, former San Antonio mayor Julian Castro and New York Mayor Bill de Blasio on subjects as varied as health care, economic inequality, climate action, gun violence, Iran and immigration.

Warren, the ideological progressive and only candidate on stage polling in double digits, knocked what she calls a rigged economy.

"Who's this economy really working for?" asked Warren, who received the first question.

"When you've got a government, when you have an economy that does great for those with money and is not doing great for everyone else, that is corruption, pure and simple," the U.S. senator and former Harvard law professor added. "We need to call it out."

With so many people on stage, candidates enjoying their first exposure to a broad national audience each had limited time to make their mark, perhaps winning a viral moment that advances their cause, draws new donors and keeps them in the headlines.

Migration crisis

But the backdrop to the debate – the mushrooming crisis on the U.S.-Mexico border, the detention of migrant children in squalid conditions and a shocking photograph of a Salvadoran man and his baby daughter drowned in the Rio Grande – led to swift, tense exchanges.

Castro, the only Latino in the race, and who unveiled a sweeping immigration plan earlier this year, called the photograph "heartbreaking." "It should also piss us all off," he said, "and it should spur us to action."

O'Rourke, Booker and later Castro notably slipped into Spanish as they addressed the migration crisis. 

De Blasio, a late entrant to the race, earned loud applause when he reminded citizens immigrants were not their enemies.

"For all the American citizens who feel you are falling behind and the American dream is not working for you, the immigrants didn't do that to you!" De Blasio boomed.

"The big corporations did that to you." Klobuchar also rushed to the defense of immigrants, saying "they do not diminish America, they are America."

O'Rourke also had a heated exchange with Castro over the separation of families and detention of migrants at the southern border. 

Castro said he would decriminalize border crossings by migrants, which he said led to the separation of families. He challenged O'Rourke and others to support him.

O'Rourke said that as a congressman he helped introduce a bill that would ensure that those who are seeking asylum and refuge in the United States are not criminalized. 

Castro responded: "I'm not talking about the ones that are seeking asylum, I'm talking about everybody else." He accused O'Rourke of not doing his homework.

Healthcare

During the debate in Miami, Warren and De Blasio were the only two candidates to raise their hands in support of eliminating private insurance. Warren said private insurance was taking advantage of Americans. She backs a government-sponsored Medicare-for-All approach and criticized those who say it is not politically feasible. 

"What they are really telling you is they just won't fight for it. Healthcare is a basic right, and I will fight for it," she said. 

But former U.S. Representative John Delaney, an outspoken critic of Medicare for All who supports a universal healthcare approach that includes private insurance, said Democrats should not throw away a system that some Americans are happy with. 

"I think we should be the party that keeps what's working and fixes what's broken," Delaney said. 

After years of defending former Democratic President Barack Obama's landmark healthcare law known as Obamacare from Republican attempts to repeal it, Democrats have struggled during the campaign to agree on the best approach to fixing it. 

The Medicare for All approach pushed by Warren and Sanders, which has gained support in Congress, would create a government-operated plan that eliminates private insurance. It is modeled on the Medicare government healthcare program for seniors. 

O'Rourke said private insurance was "fundamental to our ability to get everybody cared for," but De Blasio cut him off. 

"Congressman O'Rourke, private insurance is not working for tens of millions of Americans when you talk about the copays, the deductibles the premiums – it's not working. How can you defend a system that's not working?"

Washington state Governor Jay Inslee said he was the only candidate on the stage that had passed a public healthcare option and a law protecting a woman's right to reproductive health and health insurance.

That drew a sharp response from Klobuchar. "There are three women up here who have fought pretty hard for a woman's right to choose," she said, looking at Warren and congresswoman Tulsi Gabbard. 

Trump a target

Trump was an obvious target during the showdown, and while there was sniping among Wednesday's debaters, some trained their anger on the president, whom many of the candidates have said should face impeachment proceedings.

Gabbard savaged Trump on foreign policy, saying his "chickenhawk cabinet" has "led us to the brink of war in Iran."

Despite flying to Asia Wednesday, Trump tuned in from Air Force One and did not miss the chance to knock his would-be opponents via Twitter. 

His verdict as the evening got underway? "BORING!"

Many Americans will be watching more carefully Thursday when a clash of the old guard featuring Biden, 76, and Sanders, 77, might dominate.

The pair will face up-and-comers like Senator Kamala Harris, the only black woman in the race; Pete Buttigieg, the 37-year-old gay mayor of South Bend, Indiana; and dark horse Andrew Yang, an entrepreneur and political novice.