We heard from one New York City mayor here at the convention today, and we’ll be hearing from another later tonight. Only it’s the former mayor who got a prime-time speaking slot. Our Bobby Cuza has more on the appeal of Mike Bloomberg and what to expect from him tonight.

It’s rare that someone who’s not a candidate or a member of a major political party gets to be a keynote speaker at its national convention. But former Mayor Bloomberg occupies a unique political space. The self-made billionaire governed as a pragmatist and has supported candidates of both parties, although he’s long been a leader on liberal issues like gay rights and gun control.

New York Democrats say they welcome his endorsement of Hillary Clinton tonight, which could appeal to the political center.

"I think it is incredibly powerful that Michael Bloomberg who is nationally recognized as a balanced, centrist leader who is interested in getting problems solved is here to endorse Hillary Clinton," said New York Attorney General Eric Schneiderman. "This is an incredibly powerful message."

Bloomberg has himself flirted with presidential runs more than once, including this year. But he’s largely avoided the limelight since leaving office, returning to the helm of the business he founded, Bloomberg LP; remaining active in philanthropy and issues like climate change; and making only very rare public appearances with his successor, who ran largely on an anti-Bloomberg platform.

An outspoken critic of Donald Trump — in particular his positions on trade and immigration — Bloomberg enjoyed a good working relationship as mayor with then-Senator Clinton.

Bloomberg advisors say the key tonight is reaching independent and undecided voters.

"I think in this election, particularly with two candidates with very high negatives, people within parties are going to lineup around their parties," said Kevin Sheekey, Global Head of Communications, Government Relations and Marketing for Bloomberg LP. "And a successful campaign is going to get independents to vote for their candidate."

Once a Democrat, Bloomberg has changed his registration twice, running for mayor as a Republican then later as an Independent. In appealing to moderates, aides say his pitch will be more business-oriented than others we have heard here in Philadelphia, with Bloomberg making the case why Trump can’t be trusted with the keys to the economy. He speaks tonight after Vice President Joe Biden and just before Vice Presidential nominee Tim Kaine.