New York Mayor Mike Bloomberg endorsed Barack Obama, citing the issue of climate change.

How many votes is that worth to Obama? Well, we have here the mayor of the nation’s largest city. On top of that, he’s an independent (of sorts), and has even been a Republican, so that makes it newsy. Also, his issue preferences are very popular among a very noisy segment of the press, so it’s apt to be amplified quite a bit (not to mention the whole Bloomberg News thing).

So add up all that, and how many votes will it affect? Counting his own?


Look, endorsements aren’t apt to matter very much in general elections. I was going to do a post on this back when the Des Moines Register went from Mitt Romney recently. The logic of it is pretty straightforward; you just need to follow the causal chain on endorsements. How many people are going to even hear about the endorsement? Of those, how many support the endorser? Of those, how many are actually undecided voters? Of course, the intersection of those three groups (pay enough attention to the new to hear about the endorsement, like the endorser, undecided voter) is tiny — remember, most true undecided voters in presidential general elections don’t pay all that much attention to politics.

However, that doesn’t mean that Bloomberg is wasting his time! By linking his endorsement to a specific issue — climate — he does two things. First, he gives a pretty effective issue advertisement on the subject; Bloomberg would likely be able to get the cameras on him at any rate right now, but doing it in the context of a presidential endorsement is more effective than simply repeating what he’s said in the past on the issue.

Second, he’s essentially lobbying the president on this issue. Remember, votes don’t speak for themselves; politicians must interpret what votes mean. In that, they tend to interpret through their own experiences on the campaign trail; that is, if they’ve been talking about an issue a lot, they tend to believe that those who voted them must have endorsed that position. Most of us can’t do much about that, although perhaps more than we think — volunteer for a campaign, or if you have the means donate money, and you’ll get at least someone’s attention. But if you have a very large megaphone, you can do more, and that’s what Bloomberg is accomplishing here. Barack Obama probably knows that Bloomberg isn’t bringing any votes, but the next time he’s tempted to think that no one ever care enough to actually vote for Democrats because of climate, he’ll know for sure that at least one prominent supporter did so.

(Note: I took a break from writing this to find that Ezra Klein was tweeting up a storm with the same idea. If it becomes a post, I’ll go back and link to it).

Now, will Bloomberg’s endorsement change the politics of climate? Of course not. It’s one act. Nor will Sandy change everything…it doesn’t work like that. Some of the opposition to action on climate is partisan, and there’s nothing that anyone outside the GOP can do about that; some of it is interest-based, and that’s not going away. But if you happen to be Mike Bloomberg and you’re planning to endorse, this is almost certainly the way to get the most bang for your buck.

I’d say one other thing about it. Obama’s record on climate hasn’t been one that particularly impressed environmentalists. It is, however, clearly better than where Romney and the Republicans are from their perspective. Bloomberg’s choice demonstrates the value of signing up, as opposed to walking away. Which was going to give him a larger voice on these issues in a second Obama term: making this endorsement now, or opting to sit on his hands (or to support the Green candidate)? I think it’s almost certain that it’s the former, not the latter. The truth is that even if you’re Mike Bloomberg, you’re probably more influential if you’re on the president’s team than if you’re an outsider. And that probably only gets amplified if you have a much smaller megaphone.

[Cross-posted at A plain blog about politics]

Jonathan Bernstein

Jonathan Bernstein is a political scientist who writes about American politics, especially the presidency, Congress, parties, and elections.