Former New York City mayor Michael Bloomberg's national ad campaign includes praise from former president Barack Obama, but Bloomberg was once sharply critical of the man he's now embracing in his bid for the Democratic presidential nomination.

A new ad titled "Steady Leadership" features Obama lauding Bloomberg in 2013 as a "leader throughout the country for the past 12 years" and in 2008 for his "extraordinary leadership" in bringing people together for "pragmatic solutions." A narrator says Bloomberg and Obama worked together on gun control and improving education.

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But as mayor, Bloomberg publicly criticized Obama's "divisive populist" policies, called his first term a disappointment, allegedly called Obama the most arrogant man he'd ever met, and told friends that Republican Mitt Romney would be a superior president when the candidate challenged Obama in 2012.

Obama and Romney sought Bloomberg's endorsement in 2012, given his independent label and connections with Wall Street. The New York Times reported in June of that year that Bloomberg was overheard telling friends at a charity event that Romney would be better at running the country. However, he said he couldn't endorse Romney because of their disagreements on social issues such as abortion and gun control.

Bloomberg acknowledged he had more agreements with Obama than with Romney. However, he ripped Obama's economic rhetoric—"Who are you to say ‘Somebody else’s fair share?'" he told the Times—and criticized his lack of leadership on social issues. For example, he said then-vice president Joe Biden deserved the credit for pushing the White House to back gay marriage in 2012, a sore spot for Obama at the time.

"Let’s get serious here: it was Joe Biden that forced that issue. Some people say he just goes off; I would say he’s a principled guy," Bloomberg said, praising one of his chief rivals for the 2020 nomination.

Bloomberg waited until Nov. 1, 2012—five days before the election–to endorse Obama, pointing to Superstorm Sandy's damage to New York and Obama's stance on addressing climate change. In his endorsement, Bloomberg said he was "disappointed" in the last four years and accused Obama of "a divisive populist agenda focused more on redistributing income than creating it."

The day Bloomberg endorsed Obama in 2012, Politico published some of his sharpest attacks against Obama, which included telling the Atlantic the then-president had wrongly alienated Wall Street with his policies.

He called Obama's greatest success to date "just getting elected," and he also wasn't impressed Obama ordered the raid that killed 9/11 mastermind Osama bin Laden, saying any president would have done it.

He said the administration lacked a clear foreign policy worldview, as well.

"[There’s] no Obama Doctrine that I know of," Bloomberg said at the time. "I don’t know that anybody has enunciated a worldview the way that Henry Kissinger did in his day, or George Shultz, or even [James] Baker."

Bloomberg accused Obama of alienating Israel in 2011 with his Middle East policy address, and he suggested in 2010 in the wake of the Tea Party revolution that Obama needed better advisers.

"He campaigns ‘I'm gonna do A,' and then he doesn't do it," Bloomberg told GQ. "Now he's pissed off the supporters and the opponents. You go for it."

In 2010, Bloomberg had to deny reports that he'd told media mogul Rupert Murdoch of Obama, "I never met in my life such an arrogant man," after he and Obama played golf at Martha's Vineyard.

Bloomberg's campaign did not respond to a request for comment.

Bloomberg's embrace of Obama now makes sense politically, given Obama's high approval within the Democratic Party after two terms in office. Despite entering the 2020 race late and skipping the first four primary and caucus states, Bloomberg has quickly ascended in national and Super Tuesday state polls, thanks to his barrage of advertising.

His rise has particularly cut into Joe Biden's advantage with black voters, which was owed largely to Biden's role as Obama's vice president. Bloomberg now faces scrutiny for his support of the controversial "stop-and-frisk" policy while in office, which he has since renounced for unfairly targeting minorities.

Like Donald Trump, Bloomberg has switched parties multiple times, going from Democrat to Republican when he first ran for mayor in 2001. He became an independent in 2007 and then a Democrat again in 2018.

In 2004, when New York City hosted the Republican National Convention, Bloomberg spoke and endorsed former president George W. Bush. He backed Hillary Clinton at the 2016 Democratic National Convention and joined her party two years later.

"I know something about partisan politics. I've been them all," Bloomberg told CBS's Face the Nation in 2018.

Obama's not the most recent president Bloomberg has expressed varying sentiments about. He had kind words for Trump in 2011, telling Fox News Sunday he was a "New York icon" and a "friend."

At the time, Trump was flirting with a White House bid and pushing the conspiracy theory that Obama was born outside the United States. Bloomberg said Republicans pushing that theory were making a "terrible mistake."

Bloomberg now says Trump was always secretly mocked by their mutual New York friends.

"Behind your back they laugh at you & call you a carnival barking clown. They know you inherited a fortune & squandered it with stupid deals and incompetence," he tweeted on Thursday. "I have the record & the resources to defeat you. And I will."