[Bloomberg’s] effort, which is targeting seven battleground states where polls show Mr. Trump is likely to be competitive in November, is just one piece of an advertising campaign that is unrivaled in scope and scale. On Facebook and Google alone, where Mr. Bloomberg is most focused on attacking the president, he has spent $18 million on ads over the last month, according to Acronym, a digital messaging firm that works with Democrats. That is on top of the $128 million the Bloomberg campaign has spent on television ads, according to Advertising Analytics, an independent firm, which projects that Mr. Bloomberg is likely to spend a combined $300 million to $400 million on advertising across all media before the Super Tuesday primaries in early March. … Bloomberg’s fledgling campaign has now spent more on Google and YouTube in the past month than the Trump campaign has spent all year.

The former New York City mayor’s outsized spending has received scorn from several of his fellow White House contenders, including Sens. Bernie Sanders (I-VT) and Elizabeth Warren (D-MA).

“I’m disgusted by the idea that Michael Bloomberg or any other billionaire thinks they can circumvent the political process and spend tens of millions of dollars to buy our elections,” Sanders said last month of Bloomberg’s ad blitz.

“If you can’t build grassroots support for your candidacy, you have no business running for president,” he added. “The American people are sick and tired of the power of billionaires, and I suspect they won’t react well to someone trying to buy an election.”

During a recent campaign event in Ankeny, Iowa, Warren accused Bloomberg of attempting to “buy” the Democrat nomination.

“I am here on day two of Michael Bloomberg’s $37 million ad buy,” Warren said. “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.”