Harris is nearing the end of her veepstakes, but one rule trumps them all: Analysis

Vice President Kamala Harris is set to announce her running mate on Tuesday, but amid all the hullabaloo over who she'll tap, one mantra remains the unbreakable rule for any vice presidential search: do no harm.

Parlor talk is rampant over the three men rumored to be in the veepstakes' top tier: Govs. Josh Shapiro of Pennsylvania and Tim Walz of Minnesota and Arizona Sen. Mark Kelly. The search's calculus likely takes into account their varying appeals, backgrounds, personal baggage and where on the electoral map they can improve Harris' standing.

But it's unclear exactly how much a running mate helps the candidate at the top of the ticket -- and the downside of picking someone not ready for the bright lights of a national campaign are severe, possibly making the lack of negatives superior to any possible positives a contender brings.

"At the end of the day, the most practical thing is, do no harm," said former Sen. Doug Jones, D-Ala., a Harris ally.

"Who's the governor of which state? Who's the senator from, what state? What do they bring? There's all this public record about the other factors that you would include. But the vetting ... is where you really have to do the deep dive to make sure that somebody meets the other criteria, but that can at best bring value, at worst, be neutral, because you sure don't want someone to bring the ticket down," he added.

Those in contention to be Harris' pick have been auditioning for days, appearing across various media outlets, singing the vice president's praises and going after former President Donald Trump and Sen. JD Vance his running mate. Last weekend, some were interviewed in person at Harris' residence in Washington.

Of Shapiro, Walz and Kelly, each brings his own benefits.

Shapiro is a rising star and popular governor of the nation's marquee swing state. Walz brings a progressive record and the folksy appeal of a white-haired Midwesterner, along with an extensive record in Washington, the military and public education. Kelly boasts a sterling resume as a combat veteran and former astronaut from a swing state who is married to a survivor of political violence.

Each, too, brings vulnerabilities.

Shapiro has drawn progressive ire over his stances on Israel, school vouchers and handling of a sexual misconduct claim against a staffer in his gubernatorial office. Walz risks exacerbating attacks on Harris as a "California liberal" with his own policy record. And Kelly isn't known to exactly deliver a barnburner on the stump.

Democrats insist they're happy with their choices, arguing that any of the top-tier candidates would be positive additions to Harris' ticket.

"The stakes are very high. But fortunately for us, all three of her finalists are superstars and would do well by us," said Democratic strategist David Brand, who works with members of Harris' team and said he supports Shapiro in his personal capacity.

Still, various factors will be weighed, and downsides will be measured against upsides.

"There does seem to be a little bit of baggage around him, but again, I think that's all trumped by the very possibility, if she does pick him, that he can help lock down Pennsylvania's 19 electoral votes. That's not insignificant," one Democratic pollster said, using Shapiro as an example.

Harris "has one priority when it comes to this campaign, and it's winning the election," the person added. "She's gonna let that filter and that calculus be the only calculus in her mind when she decides who to pick. And you can rest assured that who she picks, she chose because she thought that that person helped her win the election. Nothing else."

Typically, running mates haven't moved the electoral needle significantly in a positive way, and many have enjoyed a burst of attention after their announcements before becoming largely minor factors in recent heavyweight presidential bouts.

One source familiar with the Harris campaign's thinking said a running mate has the potential to alter the race -- either by adding a benefit and complementing Harris or faceplanting, and that their potential to change the race is often underestimated. But traditionally, the person said, voters decide how to cast their ballot based on the top of the ticket.

"I think a VP can be a drag. I believe they can also provide a bump. And as is typically the case, they can have not much of an impact at all," the person said.

The downside a running mate could bring, however, could be steep.

Democratic strategists pointed to former Alaska Gov. Sarah Palin as a cautionary tale. Palin, a once-rising star in the GOP, was tapped as then-Sen. John McCain's running mate in 2008. After initially injecting his presidential campaign with a shot of youthful enthusiasm, she faltered on the national stage when her lack of policy chops was laid bare.

Her pick as his running mate has since been credited in part with McCain's loss to Barack Obama -- and Democrats are wary of a similar result, with the source familiar with the Harris campaign's thinking saying a similar stumble would be "problematic."

"I think a bad pick can weigh down that ticket," Jones added. "And given where we are in this country right now, a bad pick doesn't have to weigh down a ticket much in order to affect an outcome in a critical state. It could be two or three percentage points. It could be 10,000 votes or 20,000 votes."

The high stakes of the decision has Democrats operating behind the scenes to persuade Harris on who is the best -- and safest -- pick.

Sen. John Fetterman, D-Pa., is reportedly pushing against Shapiro, a longtime personal rival. And donors are chiming in with their own suggestions.

The backbiting has frustrated some Democrats, including Jones, who said such feuds should be dealt with in private and out of the eyes of the press and the public.

Others, though, are less concerned.

"Are they going to all jump over to support Trump tomorrow?" Brand sarcastically asked. "This always happens. I'm not real worried about it."