WASHINGTON — For Mike Bloomberg, the one-way conversation with Democratic voters is about to end.

By spending more than $400 million of his own money and largely bypassing his opponents by skipping the early primary states, Bloomberg has rocketed to double-digit support in enough national polls to qualifyfor both Wednesday night’s Nevada debate and next week’s debate in South Carolina.

But as Bloomberg’s support has risen, so has the criticism from his Democratic foes as well as the broader scrutiny of his past comments and record as New York City mayor. As he faces his rivals onstage for the first time, they’ve made it clear they’re eager to take him on.

On Tuesday, Massachusetts Sen. Elizabeth Warren offered a preview of one line of attack the billionaire can expect face to face.

“It’s a shame Mike Bloomberg can buy his way into the debate,” she tweeted, “but at least now primary voters curious about how each candidate will take on Donald Trump can get a live demonstration of how we each take on an egomaniac billionaire.”

It will be the first time he’s debated in over a decade. And the first time in this campaign that Bloomberg will have to answer before a national audience for racial and sexist comments he’s made in the past. Mark Green, the former New York City public advocate who ran against Bloomberg for mayor in 2001, says that could be tough.

“His insulting, wise-guyish comments on race and women and justice will not be easy to parry if the moderator or rival frames the questions correctly,” he said.

A new NPR/PBS NewsHour/Marist poll published Tuesday showed Bloomberg with 19% support nationally in the Democratic nominating contest, a striking figure for a candidate who has joined no debates and competed in no primaries.

The former New York City mayor, who launched his presidential campaign in November, will appear in Las Vegas alongside former Vice President Joe Biden, Sens. Warren, Bernie Sanders and Amy Klobuchar and former South Bend, Indiana, Mayor Pete Buttigieg. Fellow billionaire and philanthropist Tom Steyer is still hoping to qualify.

While Bloomberg is appearing on the debate stage in Nevada, he still is not participating in Saturday’s state caucus. He’s skipping the first four voting states — Iowa, New Hampshire, Nevada and South Carolina — in favor of focusing on the multitude of states that vote March 3, Super Tuesday.

Trying to keep expectations in check, aides have repeatedly noted in recent days that Bloomberg’s rivals have had multiple debates to hone their skills and talking points. On the campaign trail, he’s still using a teleprompter to deliver his short stump speeches, and he rarely takes questions directly from voters.

His aides have also emphasized that the former mayor is expecting fire from all angles, particularly on his status as a billionaire self-funding his campaign and on the “stop-and-frisk” police practice he employed in New York.

But Tim O’Brien, a senior adviser to the campaign, said the debate will be a chance to showcase Bloomberg’s focus and claims to deliver on key Democratic issues, like climate change and gun control.

“The debate’s a chance for us to make it clear that this is a deeply compassionate and principled man who isn’t just a rich guy on a vanity run,” O’Brien said.

Bloomberg’s opponents have telegraphed an array of attacks.

Biden has gone after him on issues relating to race, noting his past comments suggesting ending racist mortgage-lending practices known as “redlining” contributed to the financial crisis, and that Bloomberg’s ads often feature Obama prominently, though the businessman has been a critic of Obama in the past.

Klobuchar argued this weekend that voters wouldn’t want another billionaire in the White House and that her blue-collar background makes her a stronger candidate than the former mayor. Buttigieg said that Bloomberg will have to answer for reports alleging he has a long history of sexist comments and behavior in his business.

Warren and Sanders have perhaps been Bloomberg’s sharpest critics, as both see him as a useful foil to their populist campaign messages. At a campaign rally this weekend, Sanders derided Bloomberg for skipping the early primary states and mocked his riches, joking to the crowd that the businessman is “struggling, he’s down to his last $60 billion.”

But Bloomberg’s aides say he’s eager to take on Sanders, and they’ve characterized the race for the presidency as a three-way contest — between Bloomberg, Sanders and President Donald Trump.

O’Brien suggested Bloomberg will be doing more than just trying to withstand Sanders’ fire.

“I think you’re going to see us go toe-to-toe with Bernie Sanders on important issues,” he said.

“Bernie’s a millionaire, Bernie’s got a troubled record on criminal justice, he supported the 1994 crime bill,” O’Brien said. He said Sanders has previously voted to give gun makers immunity from lawsuits. Sanders has since changed his position.

Bloomberg’s other big challenge could be maintaining his cool on the debate stage amid what’s certain to be a volley of attacks from rivals and tough questions from the moderators. The former mayor has a history of becoming short or testy during press conferences, and is known for his unfiltered comments behind closed doors.

To prepare him, aides have been holding mock debates with Bloomberg in a warehouse office in downtown New York, with some of his top communications advisers playing his opponents. Senior advisers Howard Wolfson and Marcia Hale are playing Sanders and Klobuchar respectively, while Marc LaVorgna and Julie Wood, two longtime mayoral aides who now serve as campaign spokespeople, are playing Buttigieg and Warren.

Bradley Tusk, who served as Bloomberg’s campaign manager in 2009, is running the debate prep.

Green, his former mayoral opponent, said that when he debated Bloomberg the former mayor “was then what he really is now: apparently calm, confident, competent and able to memorize enough of an answer that he’ll get by,”

With expectations low, said Green, no Bloomberg booster, the average voter “will probably say ‘well, he was OK.’ “