IF YOU'RE PITTING BLOOMBERG AGAINST TRUMP, YOU'RE MAKING A CATEGORY ERROR

So there'll be a prime-time speech at the Democratic convention from Mike Bloomberg:

Michael R. Bloomberg, who bypassed his own run for the presidency this election cycle, will endorse Hillary Clinton in a prime-time address at the Democratic National Convention and make the case for Mrs. Clinton as the best choice for moderate voters in 2016, an adviser to Mr. Bloomberg said.

The news is an unexpected move from Mr. Bloomberg, who has not been a member of the Democratic Party since 2000; was elected the mayor of New York City as a Republican; and later became an independent.

But it reflects Mr. Bloomberg’s increasing dismay about the rise of Donald J. Trump and a determination to see that the Republican nominee is defeated.

 I don't know why this is "an unexpected move" from Bloomberg, whoendorsed President Obama in 2012 (though he did so late in the race and didn't speak at the convention). It's been obvious for months that he's comfortable with a Clinton presidency, but not with Trump or Bernie Sanders. As The New York Times noted in March, when Bloomberg announced that he wouldn't be running for president, 

 Had both Mr. Trump and Senator Bernie Sanders of Vermont appeared headed toward victory in the Republican and Democratic presidential primaries, Mr. Bloomberg was determined to run, according to his advisers, several of whom insisted on anonymity to speak candidly about confidential discussions.
But Mr. Bloomberg balked at the prospect of a race against Mr. Trump and Hillary Clinton, who has established a dominant lead over Mr. Sanders on the Democratic side.... Mr. Bloomberg said he could not in good conscience enter a race that could lead to a deadlock in the Electoral College -- and to the election of Mr. Trump... 

 Does it make sense for Bloomberg to speak at the convention? Most people would say yes -- but I don't see the point.
Bloomberg isn't a popular figure -- in a February CNN poll, 28% of respondents had a favorable opinion of him and 34% didn't. He's more disliked than liked by men, whites, Republicans, and older people, and if you think he might appeal to suburban women, note that is numbers are 29%/27% with women and 30%/31% with suburbanites. He's liked in the Northeast, but Clinton already has an excellent chance of sweeping all the states there, and he's disliked in other regions of the country. Moderates like him, but only by a 34%/26% margin.
So what's the point of having him speak? This, obviously: 

 ... with the Republican nominee basing his campaign on his background as a businessman, Mr. Bloomberg, a billionaire media executive and philanthropist, may help counter the Trump sales pitch. 

 But in 2016, Trump isn't running as just a businessman -- he's (dishonestly) running as a businessman who's also a class traitor. He's pretending to be a champion of the common people, and nearly half of America believes that's precisely what he is. If you want to counter Trump, you don't counter him with a businessman who's uncritical of the rich. Not this year.
Bernie Sanders will be a good foil for Trump -- a real economic populist vs. a fake. Barack Obama and Bill Clinton, too -- like Trump, they have healthy egos and star power, and they can speak as long as Trump does, but they really do know what they're talking about when they talk policy.

Bloomberg? Unless he tells some tales out of school about Trump's business failings, I don't see what he brings to the convention. He'll probably also speak in favor of immigration, and I'm certain he'll talk about the need to reform our gun laws, but there'll be plently of speakers to do that. (Bloomberg's support for gun control groups is almost certainly the reason his numbers are so low among Republicans and men.)

Warren Buffett might have been effective in this slot -- deserved or not, he has a reputation as a
billionaire with the common touch. As for Bloomberg, while I don't really think he'll send all that many voters permanently into the Jill Stein camp, I don't think he'll win many over, either.