I'm just going to start with the conclusion and say I think Hillary is going to pick Elizabeth Warren for vice-president, and the related point, that seems like a good choice. That's admittedly doing some reading of the proverbial tea leaves, and tea leaf reading has such a poor record with predicting vice-presidential picks, that I make that prediction with low confidence. I can't think of a strong counter-argument, so file that lack of confidence under "predictions are hard, especially about the future."
And certainly, I'm not in Hillary's confidence, at least not since trying to fool her with that Bill costume. You make just one bad decision, as I tried to explain to the Secret Service guy...
Warren is one of a number of people mentioned in reports based on leaks, or maybe claims of leaks, and reports based on anonymous whoever. For example, "Clinton has also begun to winnow a list of more than a dozen potential choices, another senior Democrat said." Well, if "another senior Democrat" said it, who can argue? Hillary has met with Warren more than once. Warren endorsed Hillary in an interview with Rachel Maddow, and when asked if she would be ready to be president if she was vice-president and the worst happened to Hillary, she just out and out said yes. Maybe she's just that self-confident, but that sounded like someone who had been seriously thinking about it.
Then there are the reports Senate minority leader Harry Reid is looking into Massachusetts' unusual procedure for replacing a senator. Maybe he's just idly curious. What a coincidence.
Vox looked at strength and weaknesses of list of candidates supposedly leaked. It seems a plausible list, and most names are popping up elsewhere. All the candidates have strengths and weaknesses, but what sticks out is that Warren has the strongest strengths, and the most addressable weaknesses. Others have weaknesses like lack of campaign experience, lack of governing experience, low name recognition, and to connect to my point about Reid, a bunch are incumbent senators whose replacements would be chosen by Republican governors. So if Hillary wins, a senate seat flips to the Republicans. I actually thought AL Franken and Amy Klobuchar would be considered, not just for what they might bring to the ticket, but because their replacement would be chosen by a Democratic governor. Warren's replacement, though picked by a Republican, would be temporary since Massachusetts requires a special election 160 days after the vacancy occurs, not coincidental with the next even numbered general election like most states. In other words, picking Warren entails less risk of ceding a Senate seat than if several other rumored candidates were chosen.
And here's an oddball reason for thinking Warren will get picked: Wall Street is convinced she won't be.
The main reason they think Hillary won't pick Warren is they can't stand Warren. In other words, there's some motivated reasoning going on. These are the same guys (I'm thinking "guys" is accurate) who failed to see the financial crisis of 2008 coming, who were aghast at Obama's fiscal stimulus and the Fed's monetary stimulus because they were sure hyperinfation would result. They thought Dodd-Frank was going to destroy the financial industries, and the Consumer Financial Protection Board was going to be their ruin. They're pretty much wrong about everything, except when they blame Warren for the CFPB. She does get the "blame" for that one. They're sure Hillary would be making a political mistake and that Warren knows nothing about the economy, so we can be pretty sure that means Warren is not a political mistake and does know something about economics.
As far as the weaknesses Vox spotted, in Warren's case, they have to do with Warren being critical of Hillary for switching her position on bankruptcy reform (Hillary says the bill she supported was different enough from the bill she opposed), Warren has her own platform in the Senate where she doesn't have to go along with a president like a VP will have to, and, referring back to the previous paragraph, the financial industry hates her. Vox puts that in terms of all rich people, and suggests choosing Warren might be the incentive the 1% needs to get behind Trump.
Running mates are chosen for three reasons. 1, because they bring in a certain state or region; 2, because they bring in a certain wing of the party; 3, because the presidential candidate trusts the vice presidential candidate to help govern. Paul Ryan was clearly an example of the first, not that he swung Wisconsin, and I've come to doubt vide presidents have that effect anyway. Joe Biden is an example of the third, since he came from a tiny deep blue state (maybe some Pennsylvanians were impressed he was born there) and he had no wing of the party, and his strengths as a campaigner were mostly duplicates of Obama, so Biden is clearly there because Obama trusts him. Warren would be an example of number 2, because undeniably, there's a Warren wing to the party. The disagreement over the bankruptcy law can be gotten past. The financiers are trying to apply leverage in terms of the money they won't donate if Warren is chosen, but if I was advising Hillary, I'd tell her Warren is going to bring in a lot of money too --- plus that bit above about the Wall Street guys being consistently wrong. And I wouldn't wear the Bill costume again.
One other objection, kind of the obvious one, is that this would be two women on the same ticket. Some Hillary supporters expressing this concern felt to me like they were worried about overreaching. I understand the fear, but what VP pick won't tick off somebody? I expect anyone who wouldn't vote for a ticket with two woman wouldn't vote a ticket with one woman either. Maybe some polling will prove me wrong. I will be surprised.
One job the running mate is supposed to do is be the attack dog. The one who attacks the opponent so the presidential candidate doesn't have to, or can at least do it less. If you don't know if Warren can effectively go after Trump, you are neither hearing her speeches or reading her tweets.
The one pick being pushed by the finance guys is Virginia senator Tim Kaine. Please Hillary, no. His one selling point is a Democratic governor would pick his replacement. If you think a VP candidate can bring his state along, then you'll like that Kaine comes from a swing state, but I'm as skeptical of that effect as I was a couple paragraphs ago. Kaine has the problem of having been the DNC chair who killed the 50-state strategy, while Hillary, to my great cheer, wants to revive it, even having Howard Dean on board. Kaine is also a blue dog when Hillary's problem is many Democrats doubt she's as liberal as they are. Kaine as governor didn't see an anti-abortion bill he didn't like, and Virginia's other senator, Mark Warner, praised Kaine for being really hawkish on the deficit. Well wee, that's what we need in a time of falling deficits and low interest rates, a Democratic austerian. I'll believe Kaine is serious and not like Republicans, using deficits as an excuse to cut spending and surpluses as an excuse to cut taxes --- to create the next deficit. But this isn't the time to get obsessed about the deficit.
So in sum, picking Warren means losing a senate seat but with a good chance of winning it back after a few months. It means picking an effective campaigner who knows how to frame discussions and how to stay on message. It means picking someone who helps unite the party by bringing a lot of supporters with her. Quite apart from being the risk the Wall Street guys were telling Politico she is, apart from being a desperation move (though they're right that Hillary doesn't have to make a desperation move given her strong position relative to her opponent), Warren is actually the smart move. Some other candidates would be perfectly fine, but Warren actually entails the least risk.