NEW YORK (AP) — Billionaire and former New York City Mayor Michael Bloomberg, one of the world’s richest men, has formally launched a Democratic bid for president.

Ending weeks of speculation, the 77-year-old former Republican announced his candidacy Sunday in a written statement posted on a campaign website describing himself as uniquely positioned to defeat President Donald Trump. He will quickly follow with a massive advertising campaign blanketing airways in key primary states across the U.S.

“I’m running for president to defeat Donald Trump and rebuild America,” Bloomberg wrote.

“We cannot afford four more years of President Trump’s reckless and unethical actions,” he continued. “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.”

Bloomberg’s entrance comes just 10 weeks before primary voting begins, an unorthodox move that reflects anxiety within the Democratic Party about the strength of its current candidates.

As a centrist with deep ties to Wall Street, Bloomberg is expected to struggle among the party’s energized progressive base. He became a Democrat only last year. Yet his tremendous resources and moderate profile could be appealing in a primary contest that has become, above all, a quest to find the person best-positioned to deny Trump a second term next November.

Forbes ranked Bloomberg as the 11th-richest person in the world last year with a net worth of roughly $50 billion. Trump, by contrast, was ranked 259th with a net worth of just over $3 billion. His businesses — among them are financial data services and news services in various formats — employ more than 19,000 people in 69 countries. They are also certain to raise ethical questions about how his news-oriented businesses will cover the campaign and financial conflicts of interest for a possible presidency.

Already, Bloomberg has vowed to spend at least $150 million of his fortune on various pieces of a 2020 campaign, including more than $100 million for internet ads attacking Trump, between $15 million and $20 million on a voter registration drive largely targeting minority voters, and more than $30 million on an initial round of television ads.

He did not say how much he would be willing to spend overall on his presidential ambitions, but senior adviser Howard Wolfson did: “Whatever it takes to defeat Donald Trump.”

Wolfson also said that Bloomberg would not accept a single political donation for his campaign or take a salary should he become president.

Even before the announcement was final, Democratic rivals like Bernie Sanders pounced on Bloomberg’s plans to rely on his personal fortune.

“We do not believe that billionaires have the right to buy elections,” Sanders said as he campaigned in New Hampshire on Sunday. He continued: “That is why multibillionaires like Mr. Bloomberg are not going to get very far in this election.”

Elizabeth Warren, another leading progressive candidate, also slammed Bloomberg on Saturday for trying to buy the presidency.

“I understand that rich people are going to have more shoes than the rest of us, they’re going to have more cars than the rest of us, they’re going to have more houses,” she said after a campaign stop in Manchester, New Hampshire. “But they don’t get a bigger share of democracy, especially in a Democratic primary. We need to be doing the face-to-face work that lifts every voice.”

Bloomberg does not speak in his announcement video, which casts him as a successful businessman who came from humble roots and ultimately “put his money where his heart is” to effect change on the top policy issues of the day — gun violence, climate change, immigration and equality, among them.

Bloomberg has devoted tens of millions of dollars to pursue his policy priorities in recent years, producing measurable progress in cities and states across America. He has helped shutter 282 coal plants in the United States and organized a coalition of American cities on track to cut 75 million metric tons of carbon emissions by 2025.

But he is far from a left-wing ideologue.

Bloomberg has declined to embrace Medicare for All as a health care prescription or the “Green New Deal” to combat climate change, favoring a more pragmatic approach.

Still, he has endeared himself to many of the nation’s mayors, having made huge investments to help train local officials and encouraging them to take action on climate, guns and immigration in particular.

Ahead of Bloomberg’s presidential announcement, the mayors of Columbia, South Carolina, and Louisville, Kentucky, endorsed him. Despite that show of support from at least one prominent black leader, Bloomberg may have trouble building a multi-racial coalition early on given his turbulent record on race relations in New York.

He angered many minority voters during his 12 years in the New York City mayor’s office for embracing and defending the controversial “stop-and-frisk” police strategy, despite its disproportionate impact on people of color. Facing an African-American congregation this month in Brooklyn, Bloomberg apologized and acknowledged it often led to the detention of blacks and Latinos.

The apology was received skeptically by many prominent activists who noted that it was made as he was taking steps to enter the race.

The campaign will be headquartered in Manhattan and managed by longtime adviser Kevin Sheekey. Wolfson will also play a senior role.

Bloomberg’s team did not establish a super PAC before launching the campaign, preferring to run the primary campaign and a simultaneous set of general election-focused moves like the anti-Trump internet ads and voter registration drive out of the same office.

The path ahead may be decidedly uphill and unfamiliar.

Bloomberg plans to bypass the first four states on the primary calendar — Iowa, New Hampshire, Nevada and South Carolina — and focus instead on the crush of states that vote on Super Tuesday and beyond. It’s a strategy that acknowledges the limitations of entering the race at this late stage and the opportunities afforded by his vast personal wealth.

His team has noted that several candidates have devoted much of the year to building support on the ground in the earliest states, and Bloomberg needs to be realistic about where he can make up ground.

Nearly a quarter of primary delegates are up for grabs in the March 3 Super Tuesday contests, which have gotten far less attention so far.

Bloomberg has openly considered a presidential bid before, but as an independent. He declined to enter the 2016 contest only after deciding there was no path to victory without the backing of a major political party.

He explored a run earlier this year, too, but decided there was no path with establishment-favorite Joe Biden in the race. Biden’s perceived weakness, along with the rise of progressive firebrand Warren, convinced him to reconsider.

“We believe that voters are increasingly concerned that the field is not well positioned to defeat Donald Trump,” Wolfson said of Bloomberg’s decision to change his mind.

Trump adviser Kellyanne Conway actually praised Bloomberg’s tenure as mayor when asked about his announcement Sunday on CBS’ “Face the Nation.” But she said his entrance into the 2020 race “means the Democratic field is underwhelming.”

Should Bloomberg ultimately become the nominee to take on Trump, she said, “We’re ready.”

Conway cast doubt on whether he’d be welcomed by Democratic voters.

Initially registered as a Democrat, Bloomberg, a Massachusetts native, filed paperwork to change his voter registration to Republican in 2000 before his first run for New York City mayor, according to a spokesman. In June 2007, he unenrolled from the GOP, having no formal party affiliation until he registered again as a Democrat this October.

While some will question his newfound commitment to Democrats, he vowed allegiance to the party in an Associated Press interview earlier in the year, saying, “I will be a Democrat for the rest of my life.”

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Associated Press writer Hunter Woodall in Manchester, New Hampshire, contributed to this report.