Photo Illustration: Sarah Grillo/Axios. Photos: Erik McGregor/LightRocket via Getty Images, Banaras Khan/AFP via Getty Images, and Alfredo Estrella/AFP via Getty Images

Immigration could resurface as a potent issue in the presidential election, with millions open to shifting from President Trump to Joe Biden or vice versa depending on how the issue is framed, according to data from Civis Analytics for Immigration Hub shared exclusively with Axios.

Driving the news: Immigration Hub, an advocacy group, commissioned a survey of more than 9,000 voters in Wisconsin, Michigan, Colorado and Pennsylvania to see if a voting bloc existed that could be moved toward Democrats with pro-immigration content.

  • Their findings suggest that as many as 6 million persuadable voters exist in just those states, but these "persuadables" had different collective attitudes from state to state.
  • Biden was best poised to win over more moderates in Wisconsin by showing the benefits and humanity of immigrants and appealing to American values, the survey found.
  • Trump might improve his chances of holding Pennsylvanians by hammering on "illegal" immigration as he has for years — unless Biden redefines the issue.

Why it matters: The survey found weaknesses on immigration messaging for Trump among some of the voters — including white, noncollege educated men — who put him over the top in bare victories in three of those four states in 2016.

  • Even as the coronavirus pandemic dominates voters' top concerns, the issue Trump rode to office on with chants of "Build the wall!" four years ago remains a powerful one for whichever candidate can define it.

What they're saying: "It's a vulnerability for Democrats not to talk about immigration," said Tyler Moran, executive director of Immigration Hub, which advocates for immigration and is run by several former Democratic congressional staffers.

  • Ceding it to Trump "is leaving votes on the table."

By the numbers: Nearly 3 in 10 Wisconsinites would be more likely to vote for a Democrat if shown certain pro-immigration arguments, according to Civis' predictive model.

  • The same is true for a quarter of the Michigan and Colorado populations, but less than 1 in 10 in Pennsylvania.

How it works: To help determine which voters were persuadable, survey participants were shown one of three immigration-related ads — one from the Trump campaign and two pro-immigration ads from Immigration Hub featuring a veteran and an elderly American who relies on an immigrant health worker.

The other side: While the survey targeted ways for Democrats to leverage immigration as an issue, it also confirmed that Trump's immigration rhetoric can still be extremely persuasive if unchecked — particularly in Pennsylvania.

  • "Trump actually can use immigration as a wedge with swing voters, but only if Democrats fail to articulate this alternative vision," Moran says. Democrats shouldn't necessarily make immigration their central issue, she said, but "if they say nothing, Trump fills in the blanks."

Methodology: For the study, Civis Analytics conducted online surveys and video tests with 9,639 adults in Michigan, Pennsylvania, Wisconsin and Colorado between Feb. 27 and March 24.

  • Civis used its Randomized Control Trial method f0r the video message test, which included one control group, one group that saw the Trump ad and three groups that each saw a separate pro-immigration ad created by Immigration Hub.
  • The model built to identify which respondents were "persuadable" on immigration issues relied on voter file characteristics.

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Marc Short with Katie Miller, Vice President Pence's communications director, in March. Photo: Doug Mills/The New York Times via Reuters

Marc Short, Vice President Mike Pence’s chief of staff, tested positive for the coronavirus Saturday and is quarantining, according to a White House statement.

Why it matters: Short is Pence's closest aide, and was one of the most powerful forces on the White House coronavirus task force.