That number is why Biden needs to pick Warren as his running mate: Voters may have perceived him as the most electable presidential candidate, but they didn’t see him as the best potential president of the bunch. Picking Warren would restore a sense of vision and excitement to the campaign.

For most of Biden’s career, he’s been a perfectly average Democrat. When the party was more conservative on criminal justice, foreign policy, abortion and social security, he was more conservative too. And when the party moved left, so did he. When Biden was a senator from Delaware or the right-hand man to a talented president, that was fine — he could happily follow the leaders and work toward their goals. But if Biden wants to be a great president, he needs to do more than ask “What Would Barack Do?” every day. He needs to offer voters a bigger dream than a return to the Obama era or a smattering of random compromises between conventional liberals and progressives, and he needs clear plans for how to get there.

Warren, by contrast, has had a clear mission and vision for years. She thinks that our economy is rigged in favor of the wealthy and our politics favor the powerful. And she spent much of the 2020 primary campaign laying out concrete policies to combat corruption, wealth inequality, student debt, climate change and more. Not all of Warren’s plans are perfectly clear or consistent — she took a hit in the 2020 primary when she waffled on her health-care plan and had trouble explaining how she’d pay for the one she eventually adopted — but they’re part of a largely coherent message. Biden needs that.

A Biden-Warren ticket would also keep progressives happy. Biden won the primary in part by appealing to self-described moderate and conservative Democrats, but as the nominee he has to represent the whole party. If Biden picked another relative moderate, such as Minnesota Sen. Amy Klobuchar, progressives would still grit their teeth and vote for him over Trump. But they’d start to build up resentments and become less cooperative in the next legislative session or primary election. If Biden picks Warren instead, he’ll preemptively smooth over those disagreements and magnanimously acknowledge the defeated-but-still-growing left wing of his party.

Some might worry that Warren is an electoral liability: that she’s too liberal and wouldn’t deliver a key Midwestern state like Michigan Gov. Gretchen Whitmer might be able to do. But those concerns are overblown. Americans know who Joe Biden is, and swing voters won’t suddenly conclude he’s a socialist if he picks Warren as his running mate. And Whitmer or another Midwesterner would likely give Biden a small bonus, if any, in their home state. Warren’s policy acumen is worth that small trade-off.

Other concerns about Warren are harder to wave away. She’s 70 years old and Biden is 77. One or both could have a health problem at any time. Biden and Warren have a history of sparring on policy, and they might not want to fight at work every day. And if Warren vacated her seat, Republican Gov. Charlie Baker would get to appoint a temporary replacement, potentially making it harder for Biden and Warren to pass their agenda.

But Biden doesn’t just need to win the presidential election. He needs actually be the president. So he should look past the Moneyball picks who might net him a couple votes here or there and look at candidates who have a vision, know how to make a plan and can actually govern. That’s Elizabeth Warren.