As Democrats gather in Chicago this week to rally around the daughter of immigrants from Jamaica and India as their presidential nominee, her Republican opponent will travel to the U.S.-Mexico border to highlight what he calls the “migrant invasion” and his vow to launch “the largest deportation operation in American history.”

The contrast between Vice President Kamala Harris and former President Trump illustrates what an important issue border security has become in this year’s presidential election, as Democrats and Republicans alike respond to polls showing that a growing number of voters want to stem new arrivals to the country.

On Monday night, President Biden touted the sharp reduction in border arrests since he implemented an executive action limiting asylum access, and attempted to draw out differences with Republicans’ position on the issue.

“Unlike Trump, we will not demonize immigrants, saying they are ‘poisoning the blood’ of America,” Biden said, referencing a comment Trump made last year that echoed rhetoric used by Adolf Hitler. “Kamala and I are committed to strengthening legal immigration, including protecting Dreamers and more.”

On Tuesday night, former President Obama said Harris could move the country beyond tired debates that stifle progress, because she and running mate Tim Walz “understand that we can secure our borders without tearing kids away from their parents.”

During the first two days of the Democratic National Convention, mentions of immigration were overshadowed by conversations about the COVID-19 pandemic, party unity and ways to help the working class — presenting a deep contrast to the Republican National Convention last month, when Trump supporters painted immigrants as violent criminals, drug smugglers and terrorists.

The remainder of the Democratic convention could bring more counter-messaging on immigration and the border.

Democratic strategist Michael Trujillo predicted the convention will focus on other issues.

“The border tends to be a regional issue,” he said. “I don’t know that the border is as high of a priority in Michigan, Wisconsin, Pennsylvania or Georgia.”

Republican consultant Mike Madrid said the issue is not going away.

“This is potentially the most vulnerable weak point for Kamala Harris,” Madrid said of border security. “If she can inoculate against this and have a legitimate strategy on this, her chances of winning are very good. If she doesn’t, her chances of losing are very good.”

Hoping to keep Democrats on the defense, Trump plans to visit the border in Arizona on Thursday, the same day Harris is scheduled to formally accept her nomination. His campaign said in a statement that the trip is intended to highlight that “there is no end in sight to Kamala Harris’ border crisis.”

Republicans including Trump have labeled Harris the “border czar” and blamed her for failing to stop illegal immigration. Her actual immigration policy portfolio was limited to addressing the root causes of migration in certain Latin American countries.

Last month, the Republican-led House agreed to a resolution “condemning the Biden administration and its Border Czar Kamala Harris’ failure to secure the United States border.”

At the Republican National Convention, speaker after speaker zeroed in on migration, saying it endangers public safety. Trump’s former rival Nikki Haley called it “the single, biggest threat Americans face.”

The top priority listed in the Republican Party’s 2024 platform is to “seal the border, and stop the migrant invasion.” It pledges to complete the border wall, move thousands of military troops stationed overseas to the border, reinstate the immigration policies of Trump’s first term and carry out the largest-ever deportation operation.

Democrats voted to approve their 2024 party platform on Monday, though it hadn’t been updated since Biden dropped out of the race. The platform’s chapter on immigration says a second Biden term would see him push Congress to pass legislation to codify emergency authority to temporarily stop processing most asylum claims; reform the asylum system to strengthen requirements for valid claims; increase the yearly limit of immigrant visas; and support a pathway to citizenship for long-term immigrants who lack legal documentation.

Harris recently released an ad that highlights her record as a California prosecutor and her support of the “toughest border control bill in decades.” It promises that as president, she would “hire thousands more border agents and crack down on fentanyl and human trafficking.”

At an Arizona rally earlier this month, Harris acknowledged the immigration system is broken.

“We know what it takes to fix it: comprehensive reform that includes strong border security and an earned pathway to citizenship,” she said.

She criticized Trump for pressuring House Republicans earlier this year to abandon support for a bipartisan border security agreement. “Donald Trump tanked the deal,” she said.

Harris’ support of that bill — opposed by many progressives because it did not include a path to citizenship — marked a departure from her earlier rhetoric on the issue; as a prosecutor in California and as a U.S. senator, she had developed a track record of standing up for immigrants.

GOP strategist Madrid said that shift is part of a broader pivot by many Democrats toward tougher border messaging.

In another example, while Biden in his speech played up his action limiting asylum access, he made no mention of a separate program — which took effect Monday — that would give 500,000 undocumented spouses of U.S. citizens access to a pathway to citizenship. Advocates for immigrants criticized Biden for failing to mention the policy, calling it a missed opportunity.

Madrid said that Democrats are scrambling to find the right strategy on the issue.

“This has been 180-degree turn for the Democratic Party, from how it has traditionally approached Latino voters generally and the immigration issue specifically,” he said. “It’s by design. Coupling immigration reform with border security has proven to be an unmitigated disaster for them, and they’re fixing it.”

Kerri Talbot and Beatriz Lopez, who lead the advocacy group Immigration Hub, urged Harris to strive for balanced messaging on immigration. In a memo Monday, they said the group’s research had consistently found that most people don’t know where Democrats stand on the issue, “leaving Trump and Republicans to fill in the blanks.”

The messaging that resonates most with those voters is “keeping families together,” Talbot and Lopez wrote. They also pointed to the American Civil Liberties Union’s finding that voters presented exclusively with “tough-on-immigration” messaging lose interest.

Krish O’Mara Vignarajah, president and chief executive of the immigrant advocacy organization Global Refuge, said the convention presents an opportunity for Democratic leaders to reject Republican fearmongering “and make a full-throated case that America without immigrants is no America at all.”