It has often been noted that there are a record number of women running for public office this year, but technically that's true in almost every election season that we have since we're always proceeding from a very small base thereof, so why has it been mentioned so often this year in particular? The difference is the degree.
Let's take the U.S. House of Representatives as an illustrative example. There are 235 women nominated by major parties this year for seats in the U.S. House of Representatives. In the most realistic scenario, about half of them will win election. If that were to happen, women would go from composing just 19.6% of the House to 27%, which would be an historically unprecedented single-election leap in female representation, at least in this country, and would bring us up from 104th in the world (out of 190 nations with such statistics) in this category of government representation for women to about 59th or 60th in the world, i.e. about on par with Canada, though still well behind the averages for Latin America, southern Africa, and western Europe. (We're currently trailing Saudi Arabia in this metric.)
That said, there is a clear partisan divide to be recognized here. Again taking House races as an illustration, 183 of the candidates the Democrats have nominated for House seats this year are female, as compared with only 52 of the Republican candidates for House seats. The first constitutes 42% of all Democratic House nominees, while the second constitutes only 12% of Republican nominees. This illustrates sort of how I view the major parties: both are ultimately still sexist institutions, but the Democrats far less so than the Republicans. As much speaks to what the cause of this recent surge of women running for public office is (cough, Trump, cough) and to the fact that the attitudes of the Republican Party and of Republican voters are quite a bit more sexist than those of the average American these days.
So tomorrow could be an historically important night for the women of this country, at least if Democrats do well. There has been one vaguely similar occasion that we have seen before, which was the general election of 1992, which was subsequently branded the Year of the Women because of the scale of the single-election leap in female representation in the government. It is fairly likely that tomorrow's election will be subsequently dubbed the Second Year of the Woman.