— Elizabeth Warren made a rare direct attack on a Democratic presidential rival Monday, slamming former New York Mayor Michael Bloomberg for spending millions of dollars on ads to "buy the nomination."

"I am here on day two of Michael Bloomberg's $37 million ad buy," Warren said at a community conversation in Ankeny, Iowa, Monday afternoon. "Michael Bloomberg is making a bet about democracy in 2020 -- he doesn't need people, he only needs bags and bags of money. I think Michael Bloomberg is wrong and that's what we need to prove in this election."

Warren's direct attack on Bloomberg illustrates how she plans to use another billionaire's entry into the race as fuel for her candidacy, which is aimed at addressing what Warren sees as a fundamentally unfair economic and political system that benefits the wealthy.

Bloomberg announced he was seeking the Democratic nomination on Sunday and placed at least $37 million worth of television advertising over the next two weeks, according to data from Kantar Media/CMAG.

Instead of campaigning in the early primary and caucus states -- Iowa, New Hampshire, Nevada and South Carolina -- Bloomberg is instead planning on focusing his time and resources in states with larger populations that vote on Super Tuesday.

"Think about it this way, his view is he doesn't need people who knock on doors, he doesn't need to get out and campaign with people, he doesn't need volunteers, and if you get out and knock on 1,000 doors, he'll just spend another 37 million dollars to flood the airwaves, and that's how he plans to buy the nomination in a Democratic Party," Warren said at her campaign stop. "I think it's fundamentally wrong."

She continued, "But that's exactly what's now at play in 2020. Which vision of our democracy, which version of our democracy, is going to win, and if Michael Bloomberg's version of democracy wins, then democracy changes, and it's going to be about which billionaire you can stomach going forward."

In the last few weeks, Warren has taken to slamming billionaires during her campaign stops who have complained about her two cent wealth tax during interviews on TV.

The Massachusetts senator has also only fundraised for her campaign with small dollar donations and not held fundraising events with big donors, which she promotes at each of her campaign stops.