Even with Warren's strong performance in the two-hour debate, the other candidates had their moments to control it in their attempt to gain a foothold in the unprecedentedly large field of 25 Democratic candidates.

Later, Warren said she supports a government-run health care system that could end the private insurance-based health care now used in the U.S. Some Democratic candidates and most Republicans, including Trump, oppose such a change as costly and a mistake for the country. But Warren, a former Harvard law professor, said, "Health care is a basic human right and I will fight for basic human rights."

She told a live audience in Miami, Florida, and millions more watching on national television, "I want to return government to the people." She added, referring to major corporations, "What's been missing is courage, courage in Washington to take on the giants. I have the courage to go after them."

The immediate focus Wednesday was on Sen. Elizabeth Warren, a progressive lawmaker from the northeastern state of Massachusetts who national surveys show has edged closer to Biden as a Democratic favorite to oppose Trump in the election set for Nov. 3, 2020.

Thursday's participants include former Vice President Joe Biden and other top-tier possible choices, including Senators Bernie Sanders of Vermont and Kamala Harris of California; Mayor Pete Buttigieg of the Midwestern city of South Bend, Indiana; along with six others. All twenty Democratic presidential hopefuls hope to oust Republican President Donald Trump after a single term in the White House.

Another 10 Democratic U.S. presidential contenders will debate Thursday night, including a larger number of leading candidates, following a spirited Wednesday night debate in the first major event of the 2020 election campaign.

◆ Immigration

Former U.S. housing chief Julian Castro, Sen. Cory Booker of New Jersey and other contenders called for major changes in U.S. immigration policies, voicing numerous objections to the way Trump has tried to block Central American migrants from entering the U.S. to seek asylum.

"We must not criminalize desperation" of migrants to reach the U.S., said Castro, who frequently began his answers in Spanish before repeating them in English. He said this week's photo of an El Salvadoran father and his 23-month-old daughter drowning in the Rio Grande River on the southern U.S. border with Mexico "is heart-breaking... and should piss us all off."

Warren was also joined on the debate stage by Sen. Amy Klobuchar of Minnesota, former Congressman Beto O'Rourke of Texas and five others as they parried each other's policy planks and aimed verbal shots at Trump and his 29-month White House tenure. "Immigrants do not diminish America," Klobuchar said at one point in a rejoinder to Trump, even as she added that some border restrictions must be kept to stop human traffickers.

For many Americans, it was the first chance to size up many of the Democratic presidential candidates, to see whether they might like any of them as an alternative to Trump, the country's surprise winner in the 2016 election.

The crowd in Miami, a Democratic stronghold in a state Trump won in the 2016 election, cheered raucously at verbal swipes at Trump, with Washington state Gov. Jay Inslee perhaps drawing the biggest response when he contended that Trump was the world's biggest security threat to the U.S., while the other candidates gave more traditional answers to the same question, naming Russia, China, and global warming.

The Democrats are staging a dozen debates over the coming months, well ahead of the first Democratic election contest to eventually pick the party's presidential nominee: caucus voting in the Midwest farm state of Iowa in the dead of winter next February.

The unwieldy field of candidates, in addition to another five that did not meet the Democratic National Committee's minimal political standards to merit a spot in the debates, all sense they might have a chance to unseat Trump.

Democratic voters, however, so far seem uncertain of what they are looking for in their party standard-bearer -- someone who best represents their political views on such contentious issues as health care, abortion, foreign policy, immigration, taxes and more, or possibly a candidate who has one overriding quality: the best chance of defeating Trump.