Ahead of debate, Bloomberg plays defense as Warren goes on the attack As Bloomberg preps to take his first debate stage, rivals ready to take him on

Even as he gets ready to take his first debate stage in more than a decade, former New York City Mayor Mike Bloomberg and his campaign are now girding themselves to face the gauntlet from fellow 2020 contenders.

And ahead of the big night, his opponents such as Sen. Elizabeth Warren of Massachusetts, have already signaled that he should prepare for an onslaught and are tearing into Bloomberg on two very contentious issues for his campaign: his record on race and criminal justice and how he has leveraged his wealth in his campaign.

The billionaire former mayor of New York City has not yet participated in any of the primary contests -- skipping the four early states.

“Mike Bloomberg's expansion of “stop and frisk” devastated Black and Brown communities,” Warren tweeted Tuesday afternoon. “For years, he used racist justifications to defend the practice—and more comments are already resurfacing. We need a nominee that Democratic voters can trust.”

And Warren went further.

“It’s a shame Mike Bloomberg can buy his way into the debate,” Warren 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.”

Her tweet underscores the eager, if anxious eye with which the Democratic candidates now cast toward going toe to toe with Bloomberg amid heightened scrutiny of his mayoral tenure and his rise in the polls.

“Bloomberg is the walking personification of her core message - that billionaires are trying to buy and corrupt our democracy. And also that we can't have a Democratic nominee who is bad on gender, race, and economic issues.” Adam Green, who has worked with Warren and her team since 2012 as the co-founder of Progressive Change Campaign Committee, a progressive PAC, told ABC News.

“Warren is very good at calling out villains and, you know, she will have the embodiment of a villain right there on the big stage with her,” Green said.

As opponents effectively tip their hand in how they may come at him on stage, the Bloomberg campaign has been in prep mode -- complete with mock debates, his senior staff playing the other candidates. For their part, team Bloomberg is playing offense as well.

"The opposition research on @BernieSanders could fill @realDonaldTrump’s empty Foxconn facility in Wisconsin,” Bloomberg campaign manager Kevin Sheekey tweeted Tuesday. “It is very damaging, perhaps even disqualifying."

Bloomberg has also gone on active defense on debate eve putting out two plans on two of the key issues for which he has faced intense scrutiny: criminal justice, and money. He has committed $22.5 billion to reduce prison populations by half in the next decade, pledged to invest $1 billion to support young men of color and decriminalize marijuana.

He also vows to "reform Wall Street," going so far as to name check, his primary opponent who established the Consumer Financial Protection Bureau, praising and promising to strengthen its protections. In an apparent attempt to distance himself from Wall Street, Bloomberg calls for stricter rules on banks and other financial firms, even as he built some of his vast fortune in the finance world.

For his opponents' part - Bloomberg's presence on the stage may now open up the room not just for fresh ideas -- but fresh fuel for the friction on stage for fellow contenders to take swipes at one another further: on corporate accountability, for example, something Warren's supporters feel is her sweet spot -- and Green tells ABC News, a weakness for someone like former Vice President Joe Biden.

"There are some easy pivots there," Green tells ABC. "One could argue - that Bloomberg may put more oxygen in the room."