(CNN) Tonight, round two of the first Democratic debates gets underway, with another slate of 10 candidates facing off in Miami.

Last night's debate featured strong showings from some of the lesser-known candidates, including former Housing and Urban Development Secretary Julian Castro, New York Mayor Bill de Blasio and Rep. Tulsi Gabbard of Hawaii. Sen. Elizabeth Warrenof Massachusetts, the top-polling candidate on the stage last night, is roundly seen to have set the pace, while former Congressman Beto O'Rourke of Texas turned into a target for attacks

Tonight's debate features three of the top five polling candidates in former Vice President Joe Biden and Sens. Bernie Sanders of Vermont and Kamala Harris of California. It'll also be a chance for those polling below 2%, such as Andrew Yang, Marianne Williamson, former Colorado Gov. John Hickenlooper and Sen. Michael Bennet of Colorado to introduce themselves to a national audience.

On the issues, it's likely that health care, immigration, climate change and the economy will dominate the discussion.

Between Yang's proposed universal basic income and Sanders' "Jobs for All" plan, it will be worth watching for whether more centrist candidates like Biden, Bennet and Hickenlooper push back on the party's more progressive platforms.

Several candidates may have to defend aspects of their records, including Biden on his support for the 1994 crime bill , Harris on her criminal justice record as California's attorney general and New York's Sen. Kirsten Gillibrand on her past positions on gun control and certain immigration policies . South Bend, Indiana, Mayor Pete Buttigieg will likely have to address the growing racial tension in his city over the recent shooting death of an African American man involving a police officer.

Here's a look at the candidates and some of the policies and issues they've promoted over the course of their campaigns.

Joe Biden

Even before he officially launched his campaign, the former vice president was the Democratic front-runner. Biden has maintained this position over the past few months despite a handful of controversial moments and having participated in fewer campaign events than most of his top-tier rivals. His campaign has mostly been focused on Democratic centrist ideals and policies and promises of returning to the politics under President Barack Obama.

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Health care

Biden said he supports everyone having the opportunity to get Medicare and wants to sustain the Affordable Care Act.

"One, I think that first of all, I don't believe in jettisoning the Affordable Care Act. I think we build off of it. I think we build significantly off of it and we can do a whole lot of things that we had intended to do had things been a little bit differently," he said at a town hall in May.

Biden says his plan would allow for people to keep their existing insurance. It would also allow people in Republican-led states who would have qualified for Medicaid if their states had expanded the program as the ACA permitted to have free access.

Immigration

Biden has criticized the Trump administration's "inhumane" treatment of young undocumented immigrants brought to the US as children, sometimes called Dreamers, and talks of fixing underlying issues in other countries that lead to mass immigration to the US, rather than "demonizing" immigrants coming to America.

"The fact of the matter is when I was vice president I was able to put together an overwhelming bipartisan support -- Democrats and Republicans -- to provide significant amounts of money in direct return for these countries dealing with the corrupt police systems, dealing with their school systems, dealing with the opportunities," Biden said in May.

He also says he would invest smarter in border security but is against President Donald Trump's border wall.

Climate change

Biden recently issued a policy proposal to reach net-zero emissions by 2050 through executive action.

His plan includes holding fossil fuel companies accountable, getting other countries to take action and investing in sustainable infrastructure. He's also promised safe drinking water to places like Flint, Michigan.

Biden says he'll pay for his plan by reversing Trump's corporate tax cuts, halting subsidies for fossil fuels and discouraging practices like outsourcing.

Bernie Sanders

In his second run for the White House, Sanders has doubled down on many of his policies from 2016, including universal health care, a $15 minimum wage and free tuition for public universities.

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Economy

Sanders has distilled much of his platform into what he calls an economic bill of rights that guarantees every American a job that pays a living wage, access to quality health care, a complete education, affordable housing, a clean environment and a secure retirement. On the trail, while Sanders is heavy on plans and promises, he tends to be light on details of what this will all cost.

Sanders has said that as president he would raise taxes on large companies and the wealthy, and would make significant investments in infrastructure as well as a program to guarantee a federal job for any American.

The Green New Deal, which Sanders cosponsored, would include rebuilding much of the country's infrastructure with the goal of building a "100% sustainable energy system" in the US. To do this, Sanders believes millions of workers will be required, which leads into his federal jobs guarantee program.

"When we are in the White House," Sanders' 2020 website says , "we will enact a federal jobs guarantee, to ensure that everyone is guaranteed a stable job."

The senator has also proposed a progressive tax on estates over $3.5 million, a "speculation tax" on Wall Street, increasing the marginal tax rate on incomes above $10 million and much more.

Education

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Earlier this week, Sanders released a plan to cancel all student debt (undergrad and graduate) for 45 million people. The plan would cost $1.6 trillion and be paid for, according to Sanders, by taxing financial speculation on Wall Street. The tax would include a 0.5% tax on stock trading, a 0.1% tax on bond trading and a 0.005% tax on derivative trading.

This proposal comes in addition to his plan to make public universities, trade schools and colleges tuition-free, which he estimates will cost "at least $48 billion per year."

Sanders also released a 10-point plan for public education that calls for, among other things, eliminating for-profit charter schools, providing free lunches for all public school students, creating a mandatory starting salary of $60,000 for teachers and expanding funding by $5 billion annually for after-school and summer programs.

'Medicare for All'

Sanders has been at the forefront of the push for universal health care in the US. He's introduced and co-authored multiple "Medicare for All" acts, with his most recent legislation proposed in May.

His plan would provide universal, government-run health care to all Americans. It would eliminate private insurance along with almost all copays, deductibles and premiums.

"Bottom line is Medicare is the most popular health insurance program in America, far more popular than private health insurance policies," he said in an NBC interview in June. "And we think if we expand Medicare over a four-year period to all people, you`re going to see a lot of people being very satisfied."

Estimates for the cost of Medicare for All vary, but several prominent studies place the cost to the government at $2.76 trillion to $3.87 trillion each year, according to The New York Times.

Kamala Harris

Harris' campaign has focused on three key issues: health care, immigration and gun control. The senator has defended her time as California's attorney general, in response to attacks on the tough-on-crime policies she supported during her tenure.

Health care

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Harris supports Medicare for All, and has discussed her plans for how to transition from private insurance.

"In my vision of Medicare for All there would be a phasing in of it, and there would be an option to have private insurance for supplemental," she said at a town hall in February.

She has stressed her vision of making health care affordable for everyone, focusing on reducing and eliminating costs.

Immigration

Harris has attacked Trump on numerous occasions for the administration's treatment of undocumented immigrants.

"One, we need to have a policy that is not about putting people in cages in private detention centers," she said in an interview with Telemundo in May.

Harris says she would expand deferred deportation programs and use executive action to make it easier for Dreamers to get green cards. The use of four executive actions would make it easier to adjust one's immigration status, provide an exception for those who came as children, grant work authorization to Dreamers and consider family separation an "extreme hardship."

Guns

Like other candidates, Harris said she would ban assault weapons and require universal background checks. Additionally, she favors prohibiting gun sales to domestic violence abusers.

And the gun corporation responsible would be fined up to $500,000 for each violation, providing money to put toward mental illness prevention and violence intervention programs. Harris also calls for more oversight on gun dealers who violate the law, saying she would require the Bureau of Alcohol, Tobacco, Firearms and Explosives to take their licenses.And the gun corporation responsiblewould be fined up to $500,000 for each violation, providing money to put toward mental illness prevention and violence intervention programs.

Pete Buttigieg

The 37-year-old mayor would not only be the youngest person ever elected president, but also the first one who is gay. The Harvard Rhodes Scholar served as an intelligence officer in the Navy Reserves and was deployed to Afghanistan in 2014 while he was mayor. While Buttigieg has focused much of his campaign on issues like abortion access and getting rid of the Electoral College, recently he's had to turn his attention to racial tensions in South Bend, where a recent shooting involving a police officer left a 54-year-old black man dead. The issue has taken Buttigieg off the trail and put a spotlight on his lack of support from African American voters.

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Supreme Court expansion

In a March interview with MSNBC, Buttigieg proposed expanding the Supreme Court to 15 justices as a way to create an evenly partisan court, with each of the two major parties selecting five of them. Those 10 justices would then select who sits in the remaining five seats.

"I think about the trajectory the court is on. It's being regarded increasingly as a nakedly political institution," Buttigieg said. "The question is, how do we structure it in a way that it's not going to be an apocalyptic ideological battle every time there's a vacancy?"

Health care

Buttigieg has said he supports a system in which Medicare competes with private options on the exchanges, which he believes will lead to something resembling Medicare for All, or single-payer health care.

"It will be a natural path to a Medicare for All system," Buttigieg said. "Your core health care needs to get physical and mental health care, we've learned the hard way that we can't rely on the corporate system to get that done."

Andrew Yang

The primary focus of Yang's campaign, shaped by the fear of job loss from automation, has been his proposed universal basic income for all US citizens.

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Economy

Yang's plan, called the "Freedom Dividend," would give every adult an income of $12,000 a year.

Placing a tax on top earners and a 10% tax on the production of goods and services will fund Yang's plan for a universal income. People already receiving money from welfare and social programs would choose between this or their previous benefits. Yang argues that his plan would lead to higher economic growth in the US and would lower the government's overall social safety net costs per person, which would help offset the hefty price tag of his plan. Experts have estimated that a national universal basic income plan of $10,000 per person would cost more than $3 trillion a year.

Yang also wants to rethink how the economy is measured by considering aspects like absence of substance abuse and mental health.

Medicare for All

Yang not only advocates for universal health care but also says allowing doctors to earn a flat salary instead of a price-for-service model will incentivize them.

"Health care should be a basic right for all Americans. Right now, if you get sick you have two things to worry about -- how to get better and how to pay for it. Too many Americans are making terrible, impossible choices between paying for health care and other needs. We need to provide high-quality health care to all Americans," Yang said

He calls for inclusion of holistic health care to improve the "average quality of life."

Kirsten Gillibrand

Over the past several years, the senator has shifted to the left on several issues, including gun control and immigration, both of which feature prominently in her 2020 campaign. On the trail, she has spent a particular amount of time discussing abortion.

Abortion

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Gillibrand is clear on her position: She would repeal the Hyde Amendment, which bans the use of federal Medicaid funds for most abortions except in cases of rape or incest and if there is risk to the woman's life if the pregnancy continues.

"I will not appoint a justice or a judge who doesn't believe that Roe v. Wade is settled precedent. I will work to overturn the Hyde Amendment, which makes it impossible for low-income women to get access to reproductive care, including abortion services," she said in a CNN interview in May.

She also highlighted a protection of government funding for Planned Parenthood.

Gun control

As a senator, Gillibrand has touted her "F-rating" from the National Rifle Association after flipping from her pro-gun stance as a congresswoman.

"To have a ban of bump stocks, large magazines and military-style assault weapons. I will support and try to pass anti-federal gun trafficking law, which could make a difference," she said at a meet and greet in May.

She advocates for universal background checks and closing the so-called gun show loophole.

Immigration

Gillibrand has flip-flopped on immigration, now advocating for defunding private holding facilities for undocumented migrants and rebuking Trump for the treatment of migrants crossing the border.

"In fact, what I would do is fund the border security measures that are anti-terrorism, anti-human trafficking, anti-drug trafficking, anti-gun trafficking," she said to CBS in May.

Gillibrand says she supports an increase in border security and creating easier access to immigration judges and lawyers. Recipients of the Deferred Action for Childhood Arrivals program will also be protected under her presidency, as well as the TPS program, a temporary immigration status for those fleeing countries.

John Hickenlooper

The former Colorado governor and brewery owner has positioned himself among the more moderate Democratic candidates. Hickenlooper has made his pro-capitalist stance a rallying cry, and he was met with boos when he told a crowd at California's Democratic convention that "socialism is not the answer" to beating Trump.

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Capitalism

Hickenlooper traded jabs on Twitter with Sanders in June over the merits of socialism, something he has repeatedly decried on the campaign trail. The 67-year-old pointed to his record as governor, which he said focused on small businesses and entrepreneurs, at a CNN town hall in March as a blueprint for his economic policy as president.

Hickenlooper wrote in a Wall Street Journal op-ed that he wants to strengthen antitrust enforcement, offer a tax credit for small businesses and micro-enterprises and spend $40 billion over the next 10 years on expanding apprenticeships and skills training programs. He would tax dividends and long-term capital gains at the same rate as income to pay for his economic plan.

Gun control

During his time as governor, Hickenlooper signed legislation requiring background checks for all gun purchases in Colorado -- policy he said he would make nationwide if elected. He also supports requiring people to attain licenses before being allowed to purchase any firearms.

"Why shouldn't there also be a license for buying a gun so that you have to take a test to demonstrate you know how to handle a firearm and then safely store it in the same sense?" Hickenlooper told an NPR affiliate in June. "In most states we have hunter safety classes."

Health care

The former governor has stated his opposition to a single-payer health care system, arguing that such a model would kick people off their private insurance, even if they want to keep their care. He supports the government enforcing stronger regulations to control costs and a public option for people who don't have insurance or want to change providers.

"I've said my whole life that health care should be a right and not a privilege," Hickenlooper said on CNN earlier this month. "I believe that, but I don't think we can, you know, take away private insurance from over 100 million people that want to keep it."

Eric Swalwell

As a member of the House Judiciary and Intelligence committees, Rep. Eric Swalwell of California has played a prominent role in Congress' oversight of the Russia investigation, something he has touted on the trail. The congressman has made gun control a centerpiece of his campaign, calling it a "top three issue." Swalwell has also been vocal about overhauling the nation's health care system and providing student debt relief.

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Gun control

Swalwell said he supports a government buyback program for assault weapons already in people's hands and has praised Australia's model of gun control through a mandatory buyback program. The congressman's plan also includes requiring licenses for all gun owners and a return of the 1994 ban on assault weapons.

"Last year I wrote a bill calling for a buyback and ban on assault weapons -- not just to ban future manufacturing, but to just take the 15 million that are out there and buy them back. And do what Australia did, do what New Zealand did," Swalwell told Esquire in April. "They've shown us -- Australia in the '90s, New Zealand just this week -- that courage in doing the right thing can protect people."

Health care

Swalwell said on MSNBC in March that he supports achieving "coverage for all" via a public option that keeps costs low to put pressure on private insurance companies.

"I think people want to have choices," Swalwell said. "But a public option with support from the government for those who need it the most, I think, will put pressure on the private insurers and drive down the cost."

The congressman also said he would invest a trillion dollars over the next 10 years in research for a cure for Parkinson's disease, Alzheimer's and ALS, or amyotrophic lateral sclerosis.

Student debt

The 38-year-old Swalwell said at a CNN town hall in June that he is still paying off nearly $100,000 in student loans. His proposal would offer debt-free college to public university students in exchange for four years of participation in a work-study program and a pledge to volunteer in communities of need after graduation.

"If you do work study all four years through, you learn and you earn, and then you come out and you take your first job and do volunteer service for communities that need it, it's debt-free education," Swalwell said.

Michael Bennet

In May, Bennet became the seventh senator to announce a 2020 bid for the White House. He said the clean bill of health he had received from his doctor following a prostate cancer diagnosis in March gave him clarity to seek the presidency. On the issues, Bennet counts among the more centrist candidates and has the Senate record to prove it. He's certainly a long shot, and just getting onto the debate stage is seen as a win.

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Health care

Bennet has been critical of Sanders' sweeping Medicare for All proposal, saying it would take private insurance away from millions of people who like their existing plans. Bennet has touted his health care plan called "Medicare X," which he proposed alongside Sen. Tim Kaine of Virginia.

"If you want a public option, then you can have it. Basically it's Medicare for All if you want it," Bennet said at a CNN town hall in May. "But if you want to keep the insurance you have, which many people do, you'd be able to do that as well."

Criminal justice

Prior to entering the race, Bennet signed on to legislation proposed by fellow 2020 hopeful Sen. Cory Booker of New Jersey that would legalize marijuana federally. It would also expunge the convictions of those who have already served time for their offenses. Bennet's state of Colorado was among the first to legalize recreational marijuana.

"This long-overdue change will help bring our marijuana laws into the 21st century," Bennet said in a statement . "It's past time we bring fairness and relief to communities that our criminal justice system has too often left behind."

Political revisions

As president, Bennet says, he would impose a lifetime lobbying ban for members of Congress, overturn the Supreme Court's decision in Citizens United with a constitutional amendment and push new ethics rules for elected officials, including requiring candidates for president and vice president to release 10 years of tax returns.

"We have an incredible opportunity to usher in a new era of progress," reads a statement on Bennet's campaign website. "Like generations of Americans before us, we must fix our politics and build confidence in our noble exercise in self-government."

Marianne Williamson

Oprah Winfrey once claimed to experience "157 miracles" as a result of reading self-help guru and bestselling author Williamson's 1992 book, "A Return to Love." Now, Williamson, who has racked up cable television appearances on shows like "Good Morning America" and "Real Time with Bill Maher," is hoping that her reputation as a successful author will lead her to the White House, despite having never held public office.

Reparations

Williamson discussed her plan to provide reparations to African Americans for slavery on CNN's "New Day": a $100 billion package appropriated by esteemed African American leaders over a 10-year period.

"I believe $100 billion given to a council to apply this money to economic projects and educational projects of renewal for that population is a debt to be paid," Williamson said.

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Department of Peace

The spiritual adviser has discussed "waging peace" with the creation of a US Department of Peace "as the first step in dismantling our systemically entrenched perpetuation of violence."

According to a statement on the candidate's website, the department would "address issues of peace-building here at home -- trauma informed education, community wrap around services, restorative justice, conflict resolution, mindfulness in the schools, violence prevention programs and more programs to strengthen communities and heal individuals."

Government revamp

Williamson's plan to overhaul the US political process involves support for state-by-state rejection of political gerrymandering, the elimination of voter ID requirements, a constitutional amendment to publicly finance political campaigns and lowering the voter age to 16.

This story has been updated.