Joe Biden's VP pick is a watershed moment in American democracy

This choice is historic. Given Biden's age (77), the divided state of the nation and an unprecedented set of crises, he will be selecting potentially the first female president of the United States. As a self-declared "transitional" president, he could serve just one term and then support his running mate's bid for the presidency. Biden knows what it takes to be vice-president, and wants someone who is "simpatico" with his agenda. But his decision must include a calculation as to which woman can best be described as being presidential, ready to step into the top job and knowing how to lead.

Senators Elizabeth Warren (Massachusetts), Kamala Harris (California), and Amy Klobuchar (Minnesota) were long considered the main contenders in the Veepstakes after starring in the primaries.

All three women were left disappointed when two old white men, Bernie Sanders and Joe Biden, won the acclaim from that contest - clearly the bar is set much higher for women - and Biden responded to yet another "glass ceiling moment" by declaring that he would name a woman as his running mate.

With this primary season shortened by the pandemic and postponed conventions, Biden has had more time to conduct a thorough vetting process.

The so-called "Biden List" is impressively diverse, featuring senators, congresswomen, governors and a mayor. It includes many African-American women, a Latina, a war veteran with a disability and a gay senator.

After the brutal death of George Floyd at the hands of police in Minneapolis, sparking widespread calls for a reckoning on racial injustice, Klobuchar withdrew her name from consideration. She recognised that intense scrutiny of her record as Minnesota's state attorney-general could be damaging to the campaign. She also promoted the growing calls for Biden to select a woman of colour.

This is another historic opportunity for Biden to change the dynamic of American politics by selecting a woman of colour, who is clearly made of presidential material and is capable of helping unify a country dangerously divided.

Senator Kamala Harris's background as a prosecutor and former California attorney-general makes her impressively qualified to address the police brutality which has ignited protests across the country. She was tested in the primaries, proved to be an effective campaigner and earned enough national recognition to be widely considered Biden's number one pick. There's just one big obstacle: the left wing of the Democratic Party has criticised her record on criminal justice reform, claiming she is not progressive enough. After Harris's sharp attacks on Biden during the debates, particularly suggesting he failed to support bussing to integrate schools, critics claim she has never "shown remorse" and is not a "team player". A photo taken this week of Biden's handwritten notes indicated that he would not hold grudges. One wonders whether this was an indication that he wanted to support her as a contender, or pave the way for softening the blow.

Congresswoman Val Demings (Florida), the former Orlando police chief, is equally capable. Her background in law enforcement may be a red flag as calls to "defund the police" continue. Harris or Demings, however, would be a forceful counter to Trump's self-proclaimed title as the "law and order President".

The candidate who has shot to the top of the list late in the process is Congresswoman Karen Bass (California). A former nurse and community activist who advocated for healthcare and prison reforms, Bass was the first black woman chosen as speaker of the California State Assembly. Elected to the US Congress in 2011, she has risen impressively to become chairwoman of the Congressional Black Caucus. Bass is the rare politician who appeals to progressive and moderate Democrats, while also gaining the respect of Republicans. She is applauded for her calm manner, team approach and legislative achievements, including co-authoring the George Floyd Justice in Policing Act. Bass's supporters argue that she ticks all the boxes and her selection would send a message that a Biden administration would work constructively with Congress.

The next administration will be faced with two other extraordinary challenges. Managing the pandemic and shattered economy, coupled with historic rates of joblessness, will require expertise that may determine Biden's vice-presidential choice. Senator Elizabeth Warren is well-qualified, with her strong economic and policy credentials. Governors Gretchen Whitmer (Michigan) and Michelle Lujan Grisham (New Mexico) have capably managed the pandemic in their states, winning strong approval ratings. The experience of any of these talented women could help Biden develop a national strategy with the states to change the trajectory of the coronavirus, while keeping the economy afloat.

Susan Rice, the former Obama national security advisor, is personally close to Biden and has an extensive knowledge of foreign policy and national security - though the fact that she has never held elected office and that her areas of expertise are not weak spots for Biden make her a less likely choice. Rice is also a lightning rod for conservatives, with issues ranging from her abrasive manner to her handling of the Benghazi tragedy in which four Americans, including a US ambassador, were killed in a terrorist attack on the US mission in Libya.

Other contenders such as Senator Tammy Duckworth, a double amputee and Iraq war veteran, and Tammy Baldwin, the gay senator from Wisconsin, would be hard to replace in the Senate, where the Democrats hope to gain control. Stacey Abrams and Atlanta mayor Keisha Lance Bottoms are also rising stars for future consideration for high office.

The choice of any of these highly qualified women, or even a surprise candidate, would be an important step towards cracking the White House glass ceiling.