With Joe Biden looking increasingly likely to best Bernie Sanders in the Democratic presidential primaries, it's not too early to start thinking about who would make the best running mate for the former vice president.

The electoral calculus could prove to be unusually complex this time around, yielding some seemingly obvious options — but also at least one surprising choice who could help to fortify the Democratic ticket as it heads toward its November showdown with Donald Trump.

Though pundits still often think about nominees choosing running mates to help win specific states on the electoral map, it's been a long time since that was a major factor in decision-making. In recent decades, VPs have usually been chosen to heal intra-party conflict, send a signal to the electorate about where the ticket stands ideologically, or reassure anxious general-election voters about competence.

Bill Clinton from Arkansas chose Al Gore from Tennessee to signal to the party and the country that in 1992 the Democrats were firmly rooted in the South and more ideologically moderate than they had been since the 1960s. George W. Bush tapped Dick Cheney not because his campaign worried about losing Wyoming but to allay fears that the man at the top of the ticket was a lightweight lacking in the knowledge and experience to serve as commander in chief. Barack Obama picked Biden to mollify similar concerns on the foreign policy front, not because he was eager to lock down Delaware. Finally, Donald Trump chose Mike Pence — much as Ronald Reagan had tapped George H.W. Bush and John McCain had picked Sarah Palin — to assure restive factions in the GOP that they had no reason for concern, let alone to stay home in November.

In 2020 a Biden who wins his party's nomination will need to find a running mate who could address two potential concerns. First and foremost, there are worries about his age and signs of cognitive decline. The chance that the president would only serve one term and could possibly suffer a debilitating health crisis in office would be higher than usual during a Biden administration. This points to the need to pick someone young, vital, and supremely capable of taking over the presidency.

Then there's the party and its factionalism. Despite the impressive display of consolidation among moderates on and since Super Tuesday, the Democratic Party as a whole remains fractured along both ideological and demographic lines. Biden is winning moderates, African Americans, older voters, suburban voters, and a decent number of working-class whites. Sanders, meanwhile, is winning the young, the left, and Latinos. That points to the need for Biden to pick someone to his left, and/or someone who isn't a white male. (Given the highly diverse demographics of the Democratic coalition, the days of the party running a ticket of two white men may now be permanently in the past.)

So where does that leave us?

Of the more than two-dozen candidates who ran for president this cycle, several stand out as solid choices:

Assuming she doesn't endorse Sanders for president, Massachusetts Sen. Elizabeth Warren would help excite women — above all highly educated professional women (with special emphasis on those who use Twitter). She would also be highly competent and give the campaign a wonkish, technocratic intensity while also appealing to the left-leaning voters who supported her campaign and at least some bitterly disappointed Bernie bros. On the downside, Warren's campaign dramatically underperformed, with the candidate never once finishing above third place — even in her very liberal home state. Exactly how much of an electoral boost she could offer the Biden campaign is far from clear.

Minnesota Sen. Amy Klobuchar would bolster Biden's moderate bona fides, project competence, help to ensure that her home state continues to vote blue, and maybe even contribute to the ticket's strength across the Midwest more broadly. On the other hand, Klobuchar also failed to generate much enthusiasm among voters in her run for the presidency (at least outside of Minnesota, where her endorsement of Biden the day before Super Tuesday paid off handsomely) — and there's little reason to think she would help the campaign with other demographic groups.

The presidential campaign of New Jersey Sen. Cory Booker went nowhere, despite him being widely liked in the party establishment and by many journalists and pundits. As a charismatic, smart, idealistic, and youthful African American man who works to straddle the party's neoliberal and more progressive wings, Booker would check a decent number of boxes. Whether checking those specific boxes would add much to a ticket led by the moderate-progressive who served as two-term vice president to the country's popular first-ever African American president would be an open question.

That leaves California Sen. Kamala Harris — easily the strongest choice among Biden's former competitors for the nomination. Harris has a sterling resume — criminal prosecutor, District Attorney of San Francisco, Attorney General of California, U.S. senator — and she exudes energy and compassion. She also outpolled Klobuchar and Booker for much of the time she was in the race and appears to have dropped out mainly because her bloated campaign ran out of money. Harris would contribute vigor, toughness, and an air of competence — and as a woman of color she would reflect the reality of an increasingly multicultural America better than just about anyone. That could pay lots of electoral dividends on Nov. 3.

Looking elsewhere in the party, Stacey Abrams is often floated on social media and by activists as a fabulous choice that would super-charge the Democratic electorate. I don't buy it. Abrams may have a bright future in national politics, but she's not there yet. She's an author, voting-rights activist, former Georgia state representative, failed candidate for governor, and a celebrity of sorts among woke progressives and academics. Republicans might be willing to elevate to high office underqualified media darlings who excite certain segments of the party's voters, but Democrats should aim higher and broader than that. Opting for Abrams would leave the 77-year-old at the top of the ticket looking like he's been paired with someone not quite ready for prime time.

That leaves the person who might be the best choice of all — and a true dark horse in the competition to become second in line to the most powerful job on the planet: Sixty-year-old Gov. Michelle Lujan Grisham of New Mexico. A lawyer and former member of the House of Representatives, where she served as chairwoman of the Congressional Hispanic Caucus, Lujan Grisham became the first Democratic Latina governor in the country in 2018. Along the way, she's also served as New Mexico's secretary of health. On the personal side, she shares with Biden a family history marked by tragedy: Her sister was diagnosed with a brain tumor as a child and died at age 21, while her husband (with whom she had two children) died of a brain aneurysm in 2004.

Solid experience as a legislator and chief executive, the potential to woo Hispanic voters to the polls, a compelling and relatable biography — in all of these ways, Lujan Grisham could well prove to be the perfect choice to serve as Joe Biden's running mate and potential VP.