Former New York mayor Michael Bloomberg will not run for president in 2020, the billionaire announced Tuesday.

Bloomberg flirted with a presidential run before as an independent. He registered as a Democrat last fall and spent recent months courting primary voters as a political centrist. The 77-year-old is expected to play an active role in the 2020 election from the outside. His team has been preparing a massive data-driven effort to help defeat President Donald Trump.

“I know what it takes to run a winning campaign, and every day when I read the news, I grow more frustrated by the incompetence in the Oval Office. I know we can do better as a country. And I believe I would defeat Donald Trump in a general election,” Bloomberg said in a statement. “But I am clear-eyed about the difficulty of winning the Democratic nomination in such a crowded field.”

“While there would be no higher honor than serving as president, my highest obligation as a citizen is to help the country the best way I can, right now. That’s what I’ll do, including the launch of a new effort called Beyond Carbon,” he added.

Bloomberg’s decision comes as a handful of high-profile Democrats consider joining the 2020 race. Former Vice President Joe Biden and former Rep. Robert Francis “Beto” O’Rourke (D-TX), who in recent days revealed he would announce his decision “soon,” are the most prominent holdouts. Sens. Bernie Sanders (I-VT), Kamala Harris (D-CA), Elizabeth Warren (D-MA), and Cory Booker (D-NJ) have all launched bids for the presidency and begun campaigning in key primary states like New Hampshire and South Carolina.

Bloomberg has spent hundreds of millions of dollars to promote liberal priorities on climate change, gun control, and immigration, including more than $100 million to help elect Democrats in the 2018 midterm elections.

Initially registered as a Democrat, the 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 Republican Party, having no formal party affiliation until he registered again as a Democrat last October.

In a January interview with the Associated Press, Bloomberg said if he decided to run for president, his chief priorities would be climate change, education, and public health. “Climate change could destroy the whole world and kill everyone on it,” he said. “It’s frustrating that a lot of people don’t understand that.”

The Associated Press contributed to this report.