By James Oliphant and Simon Lewis

ATLANTA (Reuters) - Democratic White House contender Pete Buttigieg, who has climbed into the lead in recent polls in Iowa, will get his turn in the spotlight on Wednesday when 10 of the top candidates for the party's presidential nomination meet in a debate in Atlanta.

The fifth debate in the race to pick a challenger to Republican President Donald Trump in the November 2020 election will also likely feature another clash over the best approach to expand health insurance coverage, with U.S. Senator Elizabeth Warren under pressure to defend her Medicare for All plan.

The Democratic debate comes just 11 weeks before the first nominating contest in Iowa on Feb. 3, raising the stakes for middle- and lower-tier candidates such as U.S. Senators Amy Klobuchar and Kamala Harris, who need to make a splash before time runs out for them.

The field of debaters has been trimmed from the 12 candidates in last month's debate. Former U.S. Representative Beto O'Rourke of Texas dropped out of the race and former U.S. Housing Secretary Julian Castro was cut from the stage by the Democratic National Committee's toughened qualifying criteria.

The debaters also could face questions about two other people who will not be on the stage - Deval Patrick, the former Massachusetts governor who jumped into the race last week, and former New York Mayor Michael Bloomberg, who is pondering a run because he is unsure if any of the current candidates can beat Trump.

The Democratic White House race has featured a three-way battle at the top of recent national polls between moderate Joe Biden, the former U.S. vice president, and progressive leaders Warren and U.S. Senator Bernie Sanders.

But Buttigieg, the moderate 37-year-old mayor of South Bend, Indiana, has taken the lead in two recent polls in the vital kickoff state of Iowa despite questions about his relative lack of experience and his inability to make inroads with African-American voters.

"This is going to be Buttigieg's turn in the spotlight, and he had better be prepared for the worst," said Aaron Kall, director of debate at the University of Michigan. "Biden and Warren have been hurt in the past debates by not being ready for the attacks."

While Buttigieg has risen in the mostly white state of Iowa, he has been plagued by questions about his relationship with the black community in South Bend, where he fired the city's first black police chief in 2012 and faced protesters earlier this year after a police officer shot a black man.

In a Quinnipiac University poll released on Monday of South Carolina, an early voting state where blacks make up about 60% of the primary electorate, Buttigieg registered no support from African-Americans, presenting a huge stumbling block to the nomination.

'DIFFERENT STANDARD'

Democratic rivals also have questioned his limited political and governing experience, with Klobuchar suggesting a female candidate with a similar resume would not have made the presidential debate stage.

"Maybe we're held to a different standard," the lawmaker from Minnesota said recently on CNN.

Warren has seen some of her momentum fade after coming under fire in the last debate from rivals who questioned how she would pay for her government-run Medicare for All plan, which would eliminate private health insurance, without raising taxes on the middle class.

The lawmaker from Massachusetts has since released a detailed plan to fund the program's $20.5 trillion in new federal spending over 10 years with tax increases on corporations and the wealthy, and "not one penny" of new middle-class taxes.

She followed up with a plan to implement her proposal in two stages, offering the option of buying into the current Medicare program for seniors, followed by legislation to end existing private plans by her third year in office.

Biden, Buttigieg and Klobuchar have questioned her proposal and offered rival plans that would allow the option of keeping private insurance or opting into a government-run plan.

Even Sanders, a Warren ally, has joined in the criticism, calling his Medicare for All plan "more progressive" than Warren's while saying his proposal would raise taxes on the middle class but lower overall healthcare costs.

Also participating in the debate will be U.S. Senator Cory Booker, U.S. Representative Tulsi Gabbard, entrepreneur Andrew Yang and billionaire activist Tom Steyer.

(Reporting by James Oliphant and Simon Lewis; Writing by John Whitesides; Editing by Colleen Jenkins and Peter Cooney)