Picking a vice president is always about winning the election. If you lose, it won’t matter who goes down with you.

But for the Democratic nominee this year, good politics matches good governance as never before, because voters’ No. 1 question will be: Is this vice presidential nominee ready to be president?

And if, as seems likely today, former vice president Joe Biden heads the ticket, voters will have a second, related question: Would we want this vice presidential nominee as our standard-bearer in 2024?

Because, whether he says so aloud or not, the best outcome for Biden and the country would be a one-term presidency that restores decency to the White House and faith to U.S. alliances, and then gives way to a new generation. The person nominated for vice president in Milwaukee in July instantly becomes the front-runner in 2024.

Two consequences flow from that.

The veep choice is sometimes thought of as a way to balance the ticket ideologically and heal a party. But if Biden, or Sen. Bernie Sanders (I-Vt.) for that matter, essentially anointed someone from the wing of the party that opposes him, the depth of his own convictions would be immediately suspect.

Second, the choice should, and almost surely will, be a woman. After watching a diverse field of promising candidates dwindle to two old white men, Democratic voters will insist on that.

But . . . which woman?

As with the vast presidential field a year ago, there is a surfeit of talent. And as with that field, when you start to examine possibilities one by one, inevitably you see weaknesses as well as strengths. That’s human nature.

You start with the senators who gained stature and name recognition competing on the presidential stage: Kirsten Gillibrand (N.Y.), Kamala D. Harris (Calif.), Amy Klobuchar (Minn.), Elizabeth Warren (Mass.). The flip side: They all lost, and they all had time to rub at least some voters the wrong way.

Then maybe you look to the governors. Gina Raimondo of Rhode Island is one of the most capable, in her second term, with a record of solving hard problems without demonizing her opponents. Flip side: Biden can probably lock down Rhode Island’s four electoral votes without Raimondo’s help.

Michelle Lujan Grisham was elected governor of New Mexico in 2018, and she knows Washington, too, having served three terms in the House. She is the first Democratic Latina to be elected as a governor, and she is a ­12th-generation New Mexican from a storied political family. On the other hand, outside New Mexico she is not a household name.

Gretchen Whitmer was also elected governor in 2018, in Michigan — the heartland, where the battle between Biden and President Trump will be truly joined. Her campaign slogan was “fix the damn roads,” which isn’t all that far from Biden’s governing philosophy and won her some notice beyond Michigan. But her entire political career has been in Lansing; will voters be satisfied with a Biden understudy without foreign or national security chops?

If the answer is yes, there’s almost-governor Stacey Abrams, who lost a close election in 2018 in Georgia. Nearly everyone who knows her or hears her comes away impressed. But will voters consider six years as minority leader of the state House of Representatives in Georgia sufficient preparation?

If so, then maybe a mayor? If City Hall-to-White House was plausible for Pete Buttigieg and Mike Bloomberg, how about Washington’s Muriel E. Bowser, in her second term, or Chicago’s Lori Lightfoot? True, she was only elected last year, but she is older than some of these other candidates, with experience as a prosecutor and a leader in police accountability.

Probably the winner will be none of the above. The political universe is wide.

But there can be no compromising on a couple of fronts. John McCain seriously undermined his credibility as Republican presidential nominee in 2008 when he chose Alaska governor Sarah Palin as his running mate.

Had he won, McCain would have been 72 when sworn in — middle-aged by this year’s standards, but old enough that voters expected him to pick a running mate ready to be commander in chief. When Palin failed that test in early vetting, McCain’s own judgment was questioned.

Biden, who will turn 78 shortly after the election, will be held to the same expectation: Choose someone who is ready — and who shares your political outlook.

The promise of Biden’s campaign is to fight for progress, not revolution; to value inclusion, not whipping up the base; and to return a basic goodness to U.S. political leadership. His running mate has to embody that promise, too.

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