Donald Trump will make this election about the border. Kamala Harris can turn a vulnerability into a strength by selecting Arizona Sen. Mark Kelly as her vice president.

Swapping a worse-for-wear 81-year-old white man for an energetic and (relatively) young Black woman at the top of the Democratic ticket has dramatically shifted the dynamics of the race in the Democrats’ favor. Harris does well with her fresh visage and soaring vision of freedom, but there is a down-to-earth issue she must confront: Trump will, as he did successfully in 2016, pound his drum on immigration, that thorniest of U.S. domestic issues. The best way for Harris to fight back is to put Kelly at her side.

Democrats are vulnerable on immigration and its festering sub-issue, the border. In multiple polls, Republicans regularly score better on immigration than Democrats, and according to a recent Gallup poll, for the first time in two decades a majority of Americans want less immigration — 55%, up from 41% a year ago. And Harris is especially vulnerable on the issue.

Within an hour of President Joe Biden dropping out of the race, the Republican National Committee posted to X a clip of Harris saying, “We’ve got to critically re-examine ICE. … And we need to probably think about starting from scratch.” The RNC asserted the comment placed Harris squarely in the Abolish ICE Movement. What’s more, Harris’ greatest responsibility as Biden’s vice president was addressing the root causes of migration from the Northern Triangle countries of Central America. The role saw Harris urging U.S. corporations to make financial investments in the Northern Triangle, which would, in theory, create jobs and stanch the push factors driving migration from those troubled countries to our southern border. By February 2023, Harris secured investment pledges of $4.2 billion from the likes of Mastercard, Visa, Nestle and Target. But Republicans used this limited assignment to dub Harris “Biden’s border czar” and tar her with responsibility for a record surge of migration to the southern border.

Putting Kelly on the Democratic ticket would serve as a bulwark against Republican attacks that Harris is weak on the border. Though Kelly is unequivocally committed to a humanitarian approach to immigration — he supports making DACA protections permanent and passing the DREAM Act, and was appalled by Trump’s family separation policy — he has distinguished himself from most elected Democrats by his intense and anguished efforts to improve border security.

Indeed, what Kelly has been able to do so forcefully is to bring border security and its reverberations forward as separate and distinct from other equally complex immigration issues. He argues, for instance, that migrant surges along the southern border are not just overwhelming the federal immigration system, but straining border municipalities that must reckon with a steady influx of new arrivals. In 2021, he joined a coalition of border-state senators, including Republican John Cornyn of Texas, in co-sponsoring a bill aimed at reimbursing border communities for the cost of rendering humanitarian services to migrants.

After Biden’s first address to Congress, in which he pledged to address the root causes of immigration from Central America, Kelly criticized Biden for not giving more focus to the immediate situation on the border, which the senator has repeatedly described as “chaos,” “a mess” and “crisis after crisis.” And in a debate with his Republican opponent in the 2022 senatorial election, Kelly called Biden’s attempt to end Title 42 “dumb,” saying such an action would create a bigger crisis at the border.

But far from just lending Harris a bit of daylight between herself and Biden’s border record, Kelly has proven an effective critic of Republicans when it comes to border issues. Earlier this year, after Senate Republicans walked away from a bipartisan bill that would have dramatically strengthened border security, Kelly tore into his Republican colleagues on the Senate floor.

“My Republican colleagues have stood on this floor, giving speeches pointing fingers at President Biden,” said Kelly. “President Biden supported the bipartisan border bill, they did not. In fact, one of my Republican colleagues said in his floor speech the other day that he hasn’t seen the two Arizona senators on this floor giving speeches about the border. To that senator, I say this: That’s because we’re not here to just talk about the problem, we’re here to do something about it.”

The Republican senators Kelly was railing against were following explicit orders from candidate Trump: Don’t give the Dems a win on immigration ahead of the November presidential election. Kelly has shown his anger at what Trump did. It’s easy to see how as a VP candidate he could turn his remarks on the Senate floor and his anger at Trump into a rousing stump speech for the Democratic ticket — a stump speech that would not only debunk the notion that Democrats are weak on border security, but reposition them as the party that’s not just here to talk about the problem, but “here to do something about it.”

Jordan Heller is a journalist and the editorial director of Ideaspace.com, a think tank focused on bipartisan solutions to immigration reform.