• Michael Bloomberg, the billionaire former mayor of New York City, officially announced on Sunday that he was running for president in 2020 as a Democrat.
  • In a statement and a video released Sunday, Bloomberg attacked President Donald Trump, a fellow wealthy New York businessman.
  • Bloomberg has had a closely watched few weeks since it was reported he was seriously contemplating a run, and he raised eyebrows across the Democratic field when it was reported he was planning to launch a $100 million TV ad campaign.

Michael Bloomberg, the billionaire former mayor of New York City, officially announced on Sunday that he was running as a Democrat in the 2020 presidential race.

In a widely released statement, Bloomberg took aim at President Donald Trump and urged voters to embark on "rebuilding America."

"I'm running for president to defeat Donald Trump and rebuild America," the statement said. "We cannot afford four more years of President Trump's reckless and unethical actions. He represents an existential threat to our country and our values. If he wins another term in office, we may never recover from the damage. The stakes could not be higher. We must win this election. And we must begin rebuilding America. I believe my unique set of experiences in business, government, and philanthropy will enable me to win and lead."

In his first ad for his campaign, Bloomberg is painted as a champion of working Americans and the middle class, and despite his $52 billion net worth, he emphasizes how different he is from Trump, a fellow New York business magnate.

The ad highlights 77-year-old Bloomberg's middle-class upbringing in Medford, Massachusetts, before the narrator said he "had to work his way through college" and built the financial-data company Bloomberg LP from "a single room to a global entity" before going on to lead job creation and development across New York City in the wake of September 11 in three terms as mayor.

Unlike Trump, Bloomberg appears to be poised to release his tax returns, as he routinely did while serving as mayor after initially refusing.

The billionaire has already had a turbulent few weeks since news broke that he was contemplating entering the race.

Last week, he appeared to take a campaign-trail-style approach in publicly acknowledging fault and apologizing for the "stop and frisk" policy practiced by New York's police force that a federal judge later ruled in 2013 violated the constitutional rights of racial minorities. Previously, Bloomberg often defended the criticized practice even after he left office.

Bloomberg has said he will self-fund his campaign.

Previous reports that Bloomberg was launching a $100 million TV ad campaign in several key primary states raised eyebrows as it marked the single biggest ad buy in American campaign history. His fellow 2020 candidates Bernie Sanders and Elizabeth Warren publicly admonished the news.

--This post originally appeared on Business Insider.