The head of an organization that has monitored women in American politics for more than 20 years hails the "history-making" selection of Senator Kamala Harris as Joe Biden's Democratic running mate in the 2020 presidential election but said more needs to be done to ensure gender equality in US politics.

"There is still an entrenched stereotype of what a successful vice-president candidate looks like in this country, because for hundreds of years it has been a straight white man," Amanda Hunter told China Daily. She is director of research and communications at the Barbara Lee Family Foundation, a nonpartisan organization aimed at advancing women's representation in politics.

"We know from more than two decades of our research that a woman faces higher standards from voters when they seek the elected office, and a woman hasn't yet occupied this office."

Harris, who is also California's former attorney general, would be the first female vice-president if Biden defeats President Donald Trump in November. She was scheduled to give her acceptance speech at the Democratic National Convention on Wednesday.

Hunter said that there is an "imagination barrier" when it comes to having a woman vice-president, "not to mention a woman president. … Senator Kamala Harris has the opportunity to throw out the rulebook and chart her own course."

It is only the third time in US history that a woman has been nominated as a presidential running mate. Harris breaks even more ground because she is the first black and Asian Indian woman to get the role.

The other two female vice-presidential candidates were Republican Sarah Palin in 2008, an Alaska governor who ran with Senator John McCain, and Democrat Geraldine Ferraro, a New York congresswoman who ran with former vice-president Walter Mondale in 1984.

Kathleen Dolan, chair of the University of Wisconsin-Milwaukee's political science department, said that "the situation of women in American politics has changed significantly since 1984 when Ferraro was the first woman nominated for vice-president. In 1984, there were 24 women in Congress. Today there are 127."

However, Ferraro, a mother of three faced an onslaught of sexism and was shamed for being a working mother. Veteran television journalist Barbara Walters accused her of being an absent mother, insinuating that her political career had gotten in the way of her looking after her children. Ferraro and her husband, John Zaccaro, denied that.

She was also pulled into messy allegations over Zaccaro's financial affairs. He was a wealthy real estate developer. She also was portrayed as incompetent on foreign policy when George H.W. Bush, Ronald Regan's running mate, goaded her during the vice- presidential debate of 1984 to explain the "difference between Iran and the embassy in Lebanon".

Most damagingly, Ferraro was seen as too weak to be president if needed. During the vice-presidential debate, one person asked Ferraro: "Do you think … the Soviets might be tempted to take advantage of you simply because you are a woman?"

In contrast, hours after Harris' selection, conservative Fox News commentator Tucker Carlson warned that Harris may "end up running the country" because of Biden's age, 77, which he said was dangerous because there was "nothing moderate" about her agenda.

Harris was also able to use her role as a stepmother of two children to her advantage, painting herself in a softer light by mentioning her stepchildren's nickname for her, "Mamala".

However, she hasn't escaped sexist and racist attacks. President Donald Trump branded her as "disrespectful … horrible" to Biden and "extraordinarily nasty" for the way she questioned Brett Kavanaugh during his confirmation hearing for the Supreme Court in 2018.

She also has faced baseless allegations by conservative law professor John Eastman who wrote in Newsweek that she could be ineligible to serve as vice-president because neither of her immigrant parents — her father was born in Jamaica and her mother in India — were US citizens prior to her birth.

That has been debunked, as Harris was born in Oakland, California, in 1964, and is considered a natural-born US citizen under the Constitution's 14th Amendment. Newsweek issued an apology.

The attack on Harris echoed lies that fueled the infamous "birther" movement that dogged former president Barack Obama. He was born in Hawaii but was accused of secretly being born in Kenya, making him ineligible to serve as president.

Dolan believes that despite such challenges, women continue to make strides in politics. Now 101 women serve in the House of Representatives. Women delegates also represent American Samoa, the District of Columbia, Puerto Rico and the Virgin Islands.

"We have had an increasing number of women run for office at all levels since then and have had the first woman candidate for president as well," she said, referring to Hillary Clinton, the Democratic nominee in 2016.

"Voters have become more accustomed to seeing women candidates, and many believe that they make better officeholders than men."