A millennial candidate has shaken up the US Democratic Party by defeating the incumbent congressman for his seat.

Alexandria Ocasio-Cortez, 28, defeated political veteran Joe Crowley, 56, on Tuesday night in their party's congressional primary in New York City.

Mr Crowley, a 10-term Democrat, had been tipped as a future party leader or even Speaker of the House.

Democratic state Comptroller Susana Mendoza says the party’s panel on sexual harassment issues will go beyond that subject to look at ways to recruit more women to run for public office.

Mendoza serves on the panel dealing with “anti-harassment and equal access” that House Speaker Michael Madigan appointed months ago amid harassment and bullying complaints in the party that he chairs.

With primary season underway and a record number of women on ballots nationwide, the question now is how many will make it to office after elections in November. The reality is that many of the women running face long odds.

Of the 40 women who have advanced from primaries in Solid Republican districts, 37 of them are Democrats, and may have the odds stacked against them.

House Republicans have doubled the number of female candidates they have recruited to run for congressional seats this year as they seek to hold their majority and counter accusations of a gender gap with Democrats.

There are 103 Republican women, including incumbents, running for House seats this election — up from 48 in the previous election cycle, according to the Center for American Women and Politics at Rutgers University.

Just 35 women filed for one of the 125 Oklahoma legislative seats that were up for election in 2012.

This year, there will be nearly four times as many women running for the same number of seats. And following a trend across the nation, women will be better represented on the ballot than in at least a decade – and likely ever.