Hillary Clinton is getting ready to make her Vice Presidential announcement. A lot of people believe it will be U.S. Senator Tim Kaine of Virginia, a conservative Democrat. They are angry that it won't be Senator Elizabeth Warren of Massachusetts.
I would not be angry if she chose Kaine.
First, people don't vote for the Vice President nominee; they vote for the Presidential nominee. An exciting candidate won't get a presidential nominee more votes for being exciting.
Second, Vice Presidents generally reflect the role the president desires them to have. Although George W. Bush and Barack Obama have had very activist Vice Presidents who have played very important organization and policy roles in their respective administrations, Hillary Clinton has talked about the Vice Presidency in the more traditional sense. So she would be wise to chose someone that fits her vision for the office.
Third, conservatives and progressives both desire to undercut Clinton's policy choices and force her more toward their policy positions. It seems to me that, rather than choose someone who is activist, or who more-progressive individuals might rally around, or who challenges her policy choices, she would be better off choosing a running mate who compliments and supports her.
Fourth, Clinton needs to strategize for the fall election. Vice Presidential choices may not win votes for the most part -- but they can help in their home states. Many running mates are chosen to add regional or political balance to the ticket, or to shore up support in a swing state. Choosing someone like Elizabeth Warren, for example, doesn't seem to help. Warren comes from a state which is already going to vote for Clinton, and Warren pulls in more-progressive voters who are going to hold their noses and vote for Clinton anyway. So what does someone like Warren get her? Nothing.
Finally, Clinton doesn't need a controversial running mate who will add to her woes and act like another lightning rod for worried moderate voters. She needs someone generally well-respected, who knows Congress, who campaigns well, who can help in the South, and who is seen as seasoned.
I'm open to a "Mondale should choose Ferrarro" argument. I see the benefits of a "wow moment" running mate. I also see the downsides, and am so far unconvinced that a "wow candidate" would help Clinton much.