Joe Biden is now the presumptive Democratic nominee for president, after Bernie Sanders suspended his campaign on Wednesday morning.

The next big question in the race - beyond when and how Mr Biden will be formally nominated amid a pandemic - is who is going to fill out the ticket as Mr Biden's running mate. The pick carries unusual importance, especially given that Mr Biden, who will turn 78 shortly after election day, would be the oldest president ever elected by far.

We already know one thing about that pick: it will be a woman, as Mr Biden pledged in a recent debate.

Below is a ranking of who makes the most sense to be that running mate.

11. Susan Rice

Hers may be the most outside-the-box name on this list, but Susan Rice has the CV: She served on the National Security Council and in a high-ranking State Department role in the Clinton administration, and she was United Nations ambassador and national security adviser in the Obama administration.

She's also an African American woman and has recently shown an interest in elective politics, considering a run against Republican senator Susan Collins this year. The one most obvious drawback here: She was in line to possibly become Barack Obama's secretary of state but withdrew after the Benghazi, Libya, attack threatened to make her confirmation “lengthy, disruptive and costly”, in her words. She had come under sharp criticism for being misleading about the nature of that attack.

That may not be a dealbreaker, but her public pronouncements turned her into a lightning rod, and Republicans would be happy to make Benghazi an issue again.

Democratic primaries: Who won where? Show all 27 1 /27 Democratic primaries: Who won where? Democratic primaries: Who won where? Arizona: Biden wins Joe Biden: 39 delegates Bernie Sanders: 28 delegates Getty Democratic primaries: Who won where? Alabama: Biden wins Joe Biden: 41 delegates Bernie Sanders: 7 delegates Michael Bloomberg: 1 delegate Reuters Democratic primaries: Who won where? Arkansas: Biden wins Joe Biden: 17 delegates Bernie Sanders: 9 delegates Michael Bloomberg: 5 delegates AFP/Getty Democratic primaries: Who won where? California: Sanders wins Bernie Sanders: 179 delegates Joe Biden: 127 delegates Michael Bloomberg: 15 delegates Elizabeth Warren: 5 delegates AP Democratic primaries: Who won where? Colorado: Sanders wins Bernie Sanders: 20 delegates Joe Biden: 9 delegates Michael Bloomberg: 9 delegates Elizabeth Warren: 1 delegate AFP/Getty Democratic primaries: Who won where? Florida: Biden wins Joe Biden: 152 delegates Bernie Sanders: 53 delegates Getty Democratic primaries: Who won where? Idaho: Biden wins Joe Biden: 11 delegates Bernie Sanders: 9 delegates EPA Democratic primaries: Who won where? Illinois: Biden wins Joe Biden: 95 delegates Bernie Sanders: 59 delegates AFP Democratic primaries: Who won where? Iowa: Buttigieg wins Pete Buttigieg: 14 delegates Bernie Sanders: 12 delegates Elizabeth Warren: 8 delegates Joe Biden: 6 delegates Amy Klobuchar: 1 delegates Reuters Democratic primaries: Who won where? Maine: Biden wins Joe Biden: 11 delegates Bernie Sanders: 9 delegates Elizabeth Warren: 4 delegates AFP/Getty Democratic primaries: Who won where? Massachussetts: Biden wins Joe Biden: 37 delegates Bernie Sanders: 29 delegates Elizabeth Warren: 25 delegates AP Democratic primaries: Who won where? Michigan: Biden wins Joe Biden: 72 delegates Bernie Sanders: 52 delegates Getty Democratic primaries: Who won where? Minnesota: Biden wins Joe Biden: 38 delegates Bernie Sanders: 27 delegates Elizabeth Warren: 10 delegates Reuters Democratic primaries: Who won where? Mississippi: Biden wins Joe Biden: 34 delegates Bernie Sanders: 2 delegates AFP via Getty Images Democratic primaries: Who won where? Missouri: Biden wins Joe Biden: 44 delegates Bernie Sanders: 24 delegates AP Democratic primaries: Who won where? Nevada: Sanders wins Bernie Sanders: 24 delegates Joe Biden: 9 delegates Reuters Democratic primaries: Who won where? New Hampshire: Sanders/Buttigieg tie Bernie Sanders: 9 delegates Pete Buttigieg: 9 delegates Amy Klobuchar: 6 delegates EPA Democratic primaries: Who won where? North Carolina: Biden wins Joe Biden: 66 delegates Bernie Sanders: 36 delegates Elizabeth Warren: 2 delegates Michael Bloomberg: 2 delegates AFP/Getty Democratic primaries: Who won where? North Dakota: Sanders wins Bernie Sanders: 8 delegates Joe Biden: 6 delegates Getty Democratic primaries: Who won where? Oklahoma: Biden wins Joe Biden: 21 delegates Bernie Sanders: 13 delegates Michael Bloomberg: 2 delegates Elizabeth Warren: 1 delegate Reuters Democratic primaries: Who won where? Florida: Biden wins Joe Biden: 152 delegates Bernie Sanders: 53 delegates Getty Democratic primaries: Who won where? Tennessee: Biden wins Joe Biden: 33 delegates Bernie Sanders: 18 delegates Michael Bloomberg: 10 delegates Elizabeth Warren: 1 delegate Reuters Democratic primaries: Who won where? Texas: Biden wins Joe Biden: 111 delegates Bernie Sanders: 102 delegates Michael Bloomberg: 10 delegates Elizabeth Warren: 5 delegates Reuters Democratic primaries: Who won where? Utah: Sanders wins Bernie Sanders: 12 delegates Joe Biden: 2 delegate Michael Bloomberg: 2 delegates AFP/Getty Democratic primaries: Who won where? Vermont: Sanders wins Bernie Sanders: 11 delegates Joe Biden: 5 delegates AP Democratic primaries: Who won where? Virginia: Biden wins Joe Biden: 66 delegates Bernie Sanders: 31 delegates Elizabeth Warren: 2 delegates AFP/Getty Democratic primaries: Who won where? Washington: Biden wins Joe Biden: 46 delegates Bernie Sanders: 43 delegates AP

10. Michelle Lujan Grisham

New Mexico's governor won't be a familiar name to many who follow national politics, nor is her state a battleground. But Michelle Lujan Grisham is among the relatively few Hispanic women who serve in high office in the United States.

9. Stacey Abrams

Ms Abrams remains a popular pick on this kind of list, given that she ran a strong campaign for Georgia governor in 2018. But she's still someone who hasn't served in any office beyond the state legislature. It also may be tempting for Mr Biden to pick her in hopes of putting an increasingly purple state in play - and some polls have suggested that's not totally outside the realm of possibility - but you do wonder how much of a priority that will be, ahead of more-competitive states.

8. Tammy Duckworth

Senator Tammy Duckworth arguably checks more boxes when it comes to her profile than anyone on this list. She's a senator and former member of the House of Representatives. She's a Purple Heart recipient who lost both of her legs in Iraq and was the first disabled woman elected to Congress. In 2018, she became the first senator to give birth while in office. And she's got a diverse background as the daughter of a Thai mother of Chinese descent.

She was one of the most hyped Democratic House candidates in the 2006 election but lost in a good Democratic year (albeit in a tough district). She was later elected to the House and went on to defeat Republican senator Mark Kirk by 14 percentage points in 2016, while Hillary Clinton carried her state by 17.

7. Val Demings

The only House member on this list, Val Demings got her first taste of the national spotlight when she served as one of the House impeachment managers. She's also an African American and former police chief of a major city: Orlando, Florida. Like Ms Duckworth in 2006, though, she was a much-hyped House candidate in the 2012 election and lost. She went on to run for mayor of Orange County, Florida, but dropped out in 2015. She has also been in federal office for just over three years.

Might one-time rival Kamala Harris be the most obvious choice? (Getty/BET) (Getty Images for BET)

6. Catherine Cortez Masto

She's the Latina politician with the best shot at being Mr Biden's pick. Senator Catherine Cortez Masto was elected to the Senate in 2016 and previously served as Nevada's attorney general for two terms. Winning Nevada shouldn't be an issue for Democrats, as it has trended to the left in recent years. But it wouldn't hurt to have an insurance policy.

5. Tammy Baldwin

This is the first pick on this list that comes from one of the true battleground states. Tammy Baldwin has served as a senator from Wisconsin since 2012, when she became the first openly gay person elected to the Senate. Two years after Mr Trump's narrow win in her state, she won reelection by 11 points in 2018.

4. Elizabeth Warren

When it comes to trying to unite the party after the Democratic primary, Elizabeth Warren might be the best pick. She overlaps with Mr Sanders on many policies and could help make sure those voters don't stay home or cross over to support Mr Trump, as some did in 2016. At the same time, she's also a septuagenarian who will turn 71 in June, which isn't ideal as a backup for Mr Biden.

As a liberal senator from Massachusetts and former Harvard University professor with demonstrated struggles over her past claims to Native American heritage, it's not difficult to see how she might be attacked.

3. Gretchen Whitmer

If Mr Biden wants a running mate who hails from one of the three key states that Mr Trump carried narrowly in 2016 - Michigan, Pennsylvania and Wisconsin - the Michigan governor makes the most sense. She's also notably been among Mr Trump's most vocal critics during the coronavirus outbreak. Mr Trump at one point said he told vice president Mike Pence not to call Ms Whitmer because of her criticism.

That's not to say she's doing this for any reason other than she's concerned about the federal response in her state, but this could be a key argument for the Biden campaign in the general election, and she's been out front on it.

2. Amy Klobuchar

Ms Klobuchar did Mr Biden a favour by dropping out of the race ahead of Super Tuesday and helping him win her state. She also earned strong reviews for her debate performances, and she has the kind of Midwestern appeal that could help in a state such as Michigan or Wisconsin. Her electoral history is pretty sterling. One drawback, though, is that she ran as a more pragmatic candidate in the primary and wouldn't necessarily appeal to liberals who feel strongly about issues such as Medicare-for-all. That said, her Senate record is unmistakably liberal.

1. Kamala Harris

There's a reason Kamala Harris tops many of these lists: She's perhaps the most logical choice. She's the only black woman serving as either a governor or senator right now. Her presidential campaign flamed out after an early surge, and given her background as a prosecutor, it is easy to see playing the traditional VP role of attacking the opposition.

At the same time, one person she attacked in rather personal terms during the primary was Mr Biden, whose past position on busing she vehemently criticised, while comparing her own experience with the issue. The main criticism of her campaign was that it wasn't really about anything, and even on busing, her position didn't wind up being much different than what Mr Biden's had been. Perhaps having her own message will be less of an issue, though, when she's running as part of a ticket.