Jennifer Lawless and Danny Hayes have conducted two studies on female candidates in politics, the first one about how the media covered them in 2012 and the second one about possible voter sexism (based on data from 2010? not sure).
The results, assuming the studies are OK (which I haven't checked), are very encouraging: Lawless and Hayes found that neither the media nor the voters in their study were particularly sexist in their treatment of politicians by gender. Gender bias is declining, in other words.
That's fantastic news, if true. Really great. On the other hand, I beg to differ on the conclusion of the summary in the Washington Post:
It might seem surprising that the media and voters aren’t to blame for women’s underrepresentation. But the data make it hard to argue otherwise.
Hayes ignores there the long incubation time to make a politician. Past media treatments of, say, Hillary Clinton and Sarah Palin may well have made some women decide not to run for office. Past voter biases have partly contributed to the current situation where women are not terribly common in the corridors of power. In other words, if the media and the voters have suddenly become completely gender-neutral, it will take time before we see the impact of that in the numbers of women getting elected to the Congress.
Women not running for office is certainly a problem, and it's important for more women to run and for others to encourage them to run. At the same time, the decision to run depends on many variables, some private and some public, and the past public treatment of a few well-known female politicians has certainly not been something that would encourage more women to run.