WASHINGTON (Reuters) - When the Democratic candidates vying for the 2020 presidential nomination convene for the second round of debates this month, there will be one new face and the opportunity for another combative exchange between the two top-tier candidates.

FILE PHOTO: Democratic U.S. 2020 election presidential candidates Senator Bernie Sanders and Senator Kamala Harris raise their hands to indicate that they would eliminate private health care as fellow candidates author Marianne Williamson, former Colorado Governor John Hickenlooper, entrepreneur Andrew Yang, South Bend Mayor Pete Buttigieg, former Vice President Joe Biden, Senator Kirsten Gillibrand, Senator Michael Bennet and Rep. Eric Swalwell listen during the second night of the first Democratic presidential candidates debate in Miami, Florida, U.S. June 27, 2019. REUTERS/Mike Segar

Here are five things to know now that the candidate lineups have been announced for the July 30 and July 31 debates in Detroit:

MONTANA GOVERNOR STEVE BULLOCK

The only new candidate on stage will be Montana Governor Steve Bullock, who is replacing U.S. Representative Eric Swalwell, who dropped out of the 2020 White House race earlier this month. Bullock trails in most opinion polls, with less than 1% support. His appearance could be a make-or-break night for Bullock as he, like many other candidates trailing in opinion polls and fundraising, seeks to make it to the third debate in September, for which the Democratic Party has set more stringent qualifying criteria.

A BIDEN-HARRIS REPRISE

A back-and-forth between former Vice President Joe Biden and U.S. Senator Kamala Harris over his record on race was one of the most contentious exchanges in the first Democratic debate, held in Miami in June. Harris, a lawmaker of black and South Asian descent and California’s former top prosecutor, saw her standing rise in opinion polls as a result. The two top-tier candidates will again share the stage on July 31. U.S. Senator Cory Booker, a black lawmaker from New Jersey who has also tussled with Biden over race, will also share the stage with Biden and Harris for the first time.

TWO PROGRESSIVES GO TOE-TO-TOE

U.S. Senators Elizabeth Warren of Massachusetts and Bernie Sanders of Vermont will share the debate stage for the first time. The two high-profile progressives from neighboring states are close in opinion polls and July 30 could be chance for one, or the other, to prove they should be the candidate of choice for liberal Democratic voters. Alternatively, the night could offer a stark contrast between their progressive policies and those of their more moderate competitors. Medicare-for-all healthcare plans will likely be in the spotlight.

WARREN’S MISSED OPPORTUNITIES

One thing you will not see during the second presidential debate series is the chance for Warren to go after either Biden or Harris. While top-tier candidates Biden and Harris shared a stage, along with Sanders, during the first debates, Warren appeared on the other night.

WHO IS THE PARTY’S RISING STAR?

Former U.S. Representative Beto O’Rourke entered the 2020 White House bid fresh off challenging Republican U.S. Senator Ted Cruz for his Texas seat in a hotly contested race he ultimately lost, but not without garnering significant national attention along the way. But 46-year-old O’Rourke finds himself eclipsed in many opinion polls by Pete Buttigieg, the 37-year-old, openly gay, mayor of South Bend, Indiana, who took a leave of absence to serve with the U.S. military in Afghanistan. The two did not share the stage during the first debate.