WASHINGTON (Reuters) - Twenty Democratic presidential hopefuls will hit the debate stage on Wednesday and Thursday nights to square off for the first time in the 2020 nominating contest.

FILE PHOTO: The line up of U.S. Democratic presidential candidates who will participate in the party's first of two nights of debate in Miami on June 26, 2019, in a combination file photos (L-R top row): U.S. Senators Cory Booker, Elizabeth Warren, Amy Klobuchar, Former U.S. Representative Beto O'Rourke, and New York City Mayor Bill de Blasio. (L-R bottom row): Former U.S. Representative John Delaney, U.S. Representatives Tim Ryan, Tulsi Gabbard, former HUD Secretary Julian Castro, and Gov. Jay Inslee. REUTERS/Files/File Photo

Each night will feature 10 candidates, putting seasoned politicians alongside fresh faces eager to introduce themselves to a national audience.

Here are some key moments to watch for during the matchups.

RACE RELATIONS

The Democratic field has the most diverse set of candidates ever to run for president, including a number of African-Americans, women and an openly gay contender.

After black turnout dipped in 2016 when Hillary Clinton was the Democratic nominee, the party is keen to energize African- American voters ahead of the November 2020 election in which Republican President Donald Trump is seeking a second term.

Some leading white contenders have faced toughed questions this month surrounding race issues - and could be forced to defend themselves on the debate stage.

Former Vice President Joe Biden was accused of insensitivity when he spoke of working with segregationists decades ago to get things done in the U.S. Senate. Pete Buttigieg, the mayor of South Bend, Indiana, grappled in the aftermath of a fatal police shooting of a black man with accusations of racism within the city’s predominately white police force.

“Never before have we seen race play this outsized role in a modern presidential campaign,” said Democratic strategist Joel Payne, who worked for Clinton’s 2016 campaign. “I would anticipate robust focus on this topic across both nights.”

DEMOCRATIC ORTHODOXY

Candidates in primary contests have long embraced more extreme positions to try to appeal to their base before moderating ahead of the general election to win over independents.

But this Democratic cycle has featured a few candidates who are bucking that trend and vocally embracing a center lane they believe will lead them to the White House.

That could lead to some fireworks. Former Colorado Governor John Hickenlooper and former U.S. Representative John Delaney, among others, are angling to push back at the more liberal flank of their party.

“I fundamentally disagree that we should do away with the democratic, regulated capitalism that has guided this country for over 200 years,” Hickenlooper said in a speech earlier this month criticizing Bernie Sanders, a senator from Vermont, who calls himself a democratic socialist.

SOFTBALL QUESTIONS

Candidates have been brushing up on their policies and rehearsing their zingers for weeks.

But the questions often unanticipated are those designed to show the candidates’ more human side. In past debates, such softball queries have sometimes stumped contenders and led to uncomfortable silences.

“There’s always a desire in highly staged events like these debates especially to try to capture that human moment,” said Joe Brettell, a Texas Republican political consultant.

“It is very difficult for a candidate who has been coached for months to have three talking points and an anecdote to then at the end of the debate, while fully mentally exhausted, relate something that is often actually awkward.”

ATTACKS

With a field this big, some strategists expect the attacks among opponents to start early and come often.

Biden, who is the front-runner, could take the bulk of the fire. Other candidates also are at risk, including U.S. Senator Elizabeth Warren, who will be the only top-five candidate appearing on the first night.

Rick Tyler, a Republican strategist who worked on U.S. Senator Ted Cruz’s 2016 presidential campaign, said Sanders had decades worth of votes in Congress to potentially criticize and a short track record when it comes to authoring legislation.

“So if I were competing in the progressive lane, I would point out that if you like Bernie’s agenda, don’t pick him to get it done because he has no record of getting anything done,” Tyler said.

BREAKING OUT

When the focus is not on the front-runners, the rest of the candidates who have struggled to get above 1% in the polls will be trying to capitalize on the national spotlight.

A standout debate moment can help skyrocket a candidate from the bottom of the polls into the top tier.

The crowded stage means limited speaking time, but getting into a back-and-forth with another candidate will generate extra time to respond.

“This may be the best opportunity for some candidates to land a punch,” Payne said. “The front-runners will be focused on narrative and values. But for those fighting for a seat at the table, this could be more of a street fight than we’re used to seeing at this stage.”

TRUMP’S TWEETS

Trump will not be on the debate stage, but he will loom large.

As Democrats make their case for replacing him, Trump may offer a live assessment. Even though he will be flying during the first debate and be in Japan for the G20 summit by the time the second set takes the stage, Trump has indicated he may respond to the events on Twitter.

If moderators take note, that could lead to the first time candidates on a debate stage get asked to respond to a presidential tweet in real time.