Why does Clinton need to chose a male running mate?

[Mister Mets]

It's safer to go with a male running mate.

The bench is bigger, especially when it comes to swing states or ethnic/ racial minorities.

And if she goes with another woman, it might be used to reinforce negative impressions of her. It could end up being a net positive if Republicans say anything stupid that helps off turn off female voters, but the Democrats may not want something with any major risks.

[Mister Mets]

And if she goes with another woman, it might be used to reinforce negative impressions of her.

What the impression that she cares about women?

They presumably wouldn't want the impression she cares about women more than men.

Hillary Clinton as a presidential contender is an inspiration to daughters.

Hillary/ Klobuchar might have to deal with accusations of radicalism.

[Mister Mets]

Why are running mates still a major part of the election?

They're not.

For the most part, the main rule is to avoid doing harm.

There may be a situation where a running mate will give a ticket credibility. For example, if John McCain had agreed to run with John Kerry in 2004.

Combining these, I'd imagine Hillary will not pick a woman, unless it can give a strong message in the GE (IE- a unity ticket with Susan Collins.) That's very unlikely.