Democrats call Donald Trump a demagogue and bad at business.NBC

Joe Biden, Michael Bloomberg, Tim Kaine, and Barack Obama were like the greatest bullpen in history last night as they came in as the ultimate relief pitchers for Hillary Clinton and her grim fight for the White House.

At the Republican convention, apart from his family, Trump hardly had a heavyweight bench, something that is likely to dog him when surrogates are needed to represent the candidate as the pace of the election quickens.

Little wonder that Hillary Clinton herself made an appearance on stage at the end of Obama's speech, rightfully paying tribute to a popular president who she needs desperately as her closer – along with his wife – to win in November.

She will be keenly aware that Al Gore ran away from President Clinton in 2000, a fatal move given that Clinton had 90 percent approval among Democrats. Having a popular president in your corner is potentially a game changer.

Obama’s speech contained the harshest criticism yet leveled at Trump, tying him in with fascists and even Jihadis such as ISIS. Obama stated, “That’s why anyone who threatens our values, whether fascists or communists or jihadists or homegrown demagogues, will always fail in the end.”

The vitriol against Trump had finally reached the fever point after two nights of relative soft attacks on Trump.

What came across from Michael Bloomberg is the view of Trump as a bad businessman, with Bloomberg dismissing Trump as a rich man’s son who had $1 million to start back in the 1960s (worth $7 million today) yet ended up in bankruptcy seven times.

Bloomberg warned people that voting for Trump was a “risky and reckless” choice.

Of all the speeches, I thought Bloomberg’s speech was the most important, hitting at the very foundation of the Trump mythology – that he is a brilliant businessman whose acute business vision can create a new way to solve political problems.

It reminded me of Senator John Kerry whose main profile was as a war hero much decorated in Vietnam when he ran against George W. Bush in 1994.

By the time the Bush machine had finished with him they had flattened Kerry’s warrior reputation to the point where it actually hurt rather than helped him.

The attack on Trump’s business expertise is a dangerous development for Trump because there is an essential truth to it. Bloomberg is the key person to make the argument, a far richer billionaire who knows in his DNA what it means to be great at business.

It is clear he has nothing but contempt for Trump, even to the point of speaking at the Democratic Party Convention and he is not even a member of the party.

There is almost an unwritten rule in New York business circles that business people rarely speak badly – publicly – of each other. I can’t recall Bloomberg making any charges against Trump before, for instance, but he is someone Bloomberg clearly despises.

As for Joe Biden and Tim Kaine, it was a good night for both. Kaine’s fluency in Spanish is clearly a major selling point among Hispanics, while Biden’s heartfelt observation that Trump’s slogan “You're Fired” said all you need to know about the man was right to the point.

With only Hillary’s acceptance speech to come, the starting gate is about to open and the real race to begin for president 2016. It will be a battle for the ages.

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