PHILADELPHIA (CBSNewYork/AP) — Former New York City Mayor Michael Bloomberg railed against Donald Trump and what he stands for during his speech at the Democratic National Convention Wednesday night.

Bloomberg, a previous Democrat who served as mayor as a Republican before turning independent, called Trump “risky, reckless and radical.”

“I’m a New Yorker, and New Yorkers know a con when we see one,” Bloomberg said. “Trump says he’ll punish manufacturers that move to Mexico or China, but the clothes he sells are made overseas in low-wage factories. He says he wants to put Americans back to work, but he games the U.S. visa system so he can hire temporary foreign workers at low wages. He says he wants to deport 11 million undocumented people, but he seems to have no problem in hiring them. What’d I miss here?” Bloomberg said.

Bloomberg referred to Trump as hypocritical.

“Truth be told, the richest thing about Donald Trump is his hypocrisy. He wants you to believe that we can solve our biggest problems by deporting Mexicans and shutting out Muslims,” Bloomberg said. “He wants you to believe that erecting trade barriers will bring back good jobs. He’s wrong on both counts.”

Bloomberg explained that Trump’s “business plan is a disaster in the making.”

“He would make it harder for small businesses to compete, do great damage to our economy, threaten the retirement savings of millions of Americans, lead to greater debt and more unemployment, erode our influence in the world, and make our communities less safe,” the former mayor said.

Bloomberg said it’s time for Americans to united to “defeat a dangerous demagogue.”

“Now, I know Hillary Clinton is not flawless — no candidate is. But she is the right choice — and the responsible choice — in this election,” he said. “No matter what you may think about her politics or her record, Hillary Clinton understands that this is not reality television; this is reality. She understands the job of president. It involves finding solutions, not pointing fingers, and offering hope, not stoking fear.”

Now a political independent, Bloomberg considered making a third-party run for president this year before opting against a campaign, expressing worry he would siphon away votes from Democratic nominee Hillary Clinton and inadvertently help elect Trump.

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“We cannot ‘make America great again’ by turning our backs on the values that made us the world’s greatest nation in the first place. I love our country too much to play a role in electing a candidate who would weaken our unity and darken our future — and so I will not enter the race for president of the United States,” Bloomberg said in March.

A three-term mayor who left office in 2013, Bloomberg has been sharply critical of Trump. He wrote in March that the real estate mogul has run “the most divisive and demagogic presidential campaign I can remember, preying on people’s prejudices and fears.”

While in office, Bloomberg had a cordial relationship with Clinton, who, as a senator from New York, was involved in the city’s post-9/11 rebuilding effort. He did, too, with Trump, who he knew from New York’s glitzy social circuit and from dealings with him as a developer.

But Trump’s hardline approach to immigration alienated Bloomberg, who often makes the case an open immigration policy is needed to keep the nation’s economy growing.

Bloomberg has also become arguably the nation’s leading gun-control advocate, spending millions of his own fortune to finance candidates and groups that call for the restriction of firearms. Trump, meanwhile, has courted the support of the National Rifle Association, a pro-gun lobbying group that frequently criticizes Bloomberg.

The Clinton campaign believes that Bloomberg’s appearance shows the breadth of support for the ex-secretary of state and will vouch for her “steady hand” on economic and national security issues.

“We are very grateful for the opportunity to have somebody like the mayor signify the broad amount of support that Hillary Clinton has earned over the course of this campaign,” said Clinton campaign spokesman Brian Fallon.

Bloomberg, worth an estimated $47 billion, is the founder of the financial news and information provider Bloomberg LP. He was a political novice when he launched an unlikely bid for mayor in 2001. Largely a social liberal but a fiscal conservative, he served for 12 years, overseeing a gilded age in the nation’s largest city even as the gap between its rich and poor grew.

(TM and © Copyright 2016 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)