JD Vance has the most to lose if Kamala Harris taps Minnesota Gov. Tim Walz as her running mate

• Vice President Kamala Harris is deliberating over her running mate selection.
• But Minnesota Gov. Tim Walz has moved to the top of the list among many Democrats.
• Walz's Midwestern sensibilities could prove to be an effective match against Vance, an Ohioan.

Whoever emerges as Vice President Kamala Harris' running mate has the potential to dramatically reset the 2024 presidential race.

After former President Donald Trump selected Ohio Sen. JD Vance as his vice-presidential pick, Republicans were thrilled that the GOP lawmaker's Midwestern roots and working-class upbringing would set him apart from what was previously thought to be President Joe Biden's reelection effort alongside Harris.

But Harris, who's now in the driver's seat as the presumptive Democratic nominee, is currently mulling over several potential picks, which reportedly includes two-term Minnesota Gov. Tim Walz.

Walz, a Nebraska native and former congressman, is seen by many Democrats as an effective messenger who'd be able to connect with rural and working-class voters that have drifted away from the party in recent years.

Should Harris select Walz, it'd indicate her intent to compete hard in the key battlegrounds of Michigan, Pennsylvania, and Wisconsin. And the move could put Vance on the defense in Midwest, a position that the GOP didn't foresee when he was selected by Trump.

Walz is already on offense

Harris has been the presumptive Democratic presidential nominee for just over a week following President Joe Biden's decision to exit the race. But even when Biden was still in the race, Walz zeroed in on Vance.

And in a recent appearance on "Morning Joe," he didn't let up.

"People like JD Vance know nothing about small-town America," Walz said. "My town had 400 people in it, 24 kids in my graduating class — 12 were cousins."

"He gets it all wrong," he continued. "It's not about hate … the golden rule there is mind your own damn business."

Walz then described both Vance and Trump as "robber barons" who have done more harm than good to the Midwest.

The governor in multiple appearances has also throttled the GOP ticket on everything from abortion and book bans to funding for public education and IVF. And he's repeatedly described Vance as "weird."

Walz intrigues many Democrats as they look for a surrogate who can rally base voters, connect with union workers, and potentially hold the support that Biden garnered from seniors.

For more than a year, Democrats felt weighed down by Biden's inability to find success in selling his economic record. But Walz has no qualms about leaning into concerns over health care costs, the sort of populist issue that can win crossover support.

The political map has evolved

By the time Biden had left the race, he was trailing in Michigan and Pennsylvania, while keeping things relatively close in Wisconsin.

But the momentum was on the GOP side.

With Harris' ascension in the race, her candidacy has seemingly opened up more electoral avenues for Democrats, as her stronger appeal with younger voters and minorities could help her win Sun Belt states like Arizona, Georgia, Nevada, and North Carolina.

A Walz selection has the potential to essentially nullify what was thought to be a Vance advantage across the Midwest.

Vance, a first-term lawmaker best known for his memoir, "Hillbilly Elegy," is in many ways defined by his association with the region.

However, Walz affords Democrats an authentic Midwestern voice, something that could throw Republicans off-message and be trickier to navigate should the governor emerge as the nominee.

Walz is no stronger to agricultural and farming interests, an issue that national Democrats in recent years struggled to play up as they lost rural support. The governor gives the party the sort of geographical diversity that counteracts Harris' background as a Californian who cut her political teeth in the San Francisco Bay Area.

And such a Democratic ticket could force Vance to campaign even harder in Midwestern locales that Republicans previously thought were theirs for the taking. It could also keep Vance from campaigning in areas where Trump remains weak, namely in the suburbs.

Vance so far has been an unpopular figure

Another advantage that Walz would likely have over Vance is the Ohioan's rough national rollout among the general electorate.

Even as Vance won his Senate race in 2022, his single-digit margin of victory was weaker than that of other statewide Republicans on the ballot that year.

After the Republican National Convention in July, Vance failed to get the sort of bounce that vice-presidential selections usually receive from voters — notably in the Midwest.

CNN in a July survey found that Vance had a 28% favorable rating and a 44% unfavorable rating among registered voters in Illinois, Indiana, Michigan, Ohio, and Wisconsin. This result gave him a minus-16-point favorability rating in the very region where Republicans are counting on him to draw in voters.

Should Walz be selected and lift Harris' standing in the region, it could be the turning point of the race, when the ticket seemingly shifted what looked like a GOP edge into one where Democrats became more competitive up and down the ballot.

It's not the scenario that Republicans envisioned. But with Walz on the Democratic ticket, it could become a reality.