For the last few months, Michael Bloomberg has been not-so-quietly mulling a run for the White House. But the billionaire former New York City mayor announced today (March 7) that he would not enter the 2016 race, citing fears that his third-party candidacy might result in victory for Donald Trump or Ted Cruz.

“As the race stands now, with Republicans in charge of both Houses, there is a good chance that my candidacy could lead to the election of Donald Trump or Senator Ted Cruz,” he wrote in a column for Bloomberg View. “That is not a risk I can take in good conscience.”

Bloomberg did get quite close to making a presidential run, with his team producing a video ad (see above) that would have launched his campaign.

The billionaire’s move is a tacit endorsement of former secretary of state Hillary Clinton. Bloomberg’s team of pollsters determined that he would  have a fighting chance against Trump and senator Bernie Sanders, but that a contest against Trump and Clinton could result in no candidate receiving the 270 electoral votes required to win the presidency. That would send the election to the House of Representatives, where Republicans hold a significant majority.

Bloomberg said that Trump “has run the most divisive and demagogic presidential campaign I can remember, preying on people’s prejudices and fears,” and that Cruz’s anti-immigrant and anti-Muslim rhetoric “may be less bombastic than Trump’s position, but it is no less divisive.”

He does not mention Clinton and Sanders by name, other than to say: “The leading Democratic candidates have attacked policies that spurred growth and opportunity under President Bill Clinton—support for trade, charter schools, deficit reduction and the financial sector.”