Jonathan Bernstein: “One is that the upside is limited: It’s simply not likely to win a lot of votes. Nomination voters are picking a nominee, not a ticket. The reason that Castro is available as a potential running mate, along with two dozen other hopefuls who dropped out either before or after formally declaring their candidacies, is that they all failed to win enough support to continue their campaigns. They simply don’t command votes to supply to the top of the ticket.”
“There’s more, however. One of the problems with having a vice-presidential nominee during primaries and caucuses is that it opens up new lines of attack… And nomination voters are more likely than general-election voters to be sensitive to small differences in policy preferences. General-election voters, after all, mostly vote based on party. Voters in primaries are looking for ways to sort through and eliminate candidates, and a bad vote or action in a running mate’s past could supply an easy way to narrow the field.”
“By the way, a lot of this logic applies as well to the pundit fantasy that a nominee would name a cabinet during the campaign — another thing that might be appealing in the abstract, but wouldn’t help a candidate succeed.”
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