BURLINGTON, Iowa — Joe Biden’s campaign is not anchored in a big policy idea like Bernie Sanders’ Medicare for All. He is not proposing transformative change like Elizabeth Warren. Instead, Biden’s call to voters is a more visceral one, casting the 2020 race as a test of the country’s character.

The recent back-to-back mass killings in Texas and Ohio have, for now, allowed Biden to re-center his campaign on those ideas. After spending the past three months largely on defense over a long policy record that draws fire from Democratic Party’s most progressive corners, Biden reasserted himself this week with a blistering takedown of President Donald Trump’s racist language and the ways in which some of the Republican president’s anti-immigrant outbursts could have inspired one of the shootings.

“I will not let this man be reelected president of the United States of America,” Biden said this week in Iowa, where he weaved between hushed disappointment and incredulous fury over a president who offers “no moral leadership.”

Biden has hardly been alone among Democratic presidential candidates in assailing Trump after the latest killings. The shooting suspect in El Paso has been linked to a racist screed that echoed many of the president’s own tirades about an immigrant “invasion,” prompting at least two of Biden’s rivals to brand Trump a “white supremacist.”

Yet only Biden has made questions of character — that of Trump and the nation — the centerpiece of his White House bid. He says it was Trump’s equivocating response to the 2017 racial clash in Charlottesville, Virginia, that prompted him to run and he has repeatedly declared the election a battle “for the soul of the nation.”

The approach has risks as Biden has faced months of criticism for his own past handling of issues related to race and gender. He found himself on the defensive again Thursday night when he told an audience in Des Moines that “poor kids are just as bright and just as talented as white kids.”

He immediately sought to clarify his remarks, adding “wealthy kids, black kids, Asian kids.”

The 76-year-old would be the oldest new president in history — 78 upon inauguration. And his positions on a range of issues, including abortion access and criminal justice, have evolved along with his party over the past four decades, subjecting him to bruising criticism from progressives.

Biden’s advisers contend that those past policy positions will matter less to most voters, both in the Democratic primary and the general election, than their assessments of Trump’s moral fitness for the job.

In Iowa this week, Biden tore into what he sees as Trump’s shortcomings on that front.

“The words of a president matter,” he said in a Wednesday speech. “They can appeal to the better angels of our nature. But they can also unleash the deepest, darkest forces in this nation.”

At the Iowa State Fair a day later, Biden said, “Everything the president’s said and done encourages white supremacists.”

His words resonated with Staci Beekhuizen, a teacher in Lee County, Iowa, who called Biden’s Wednesday address “presidential.”

“The vice president showed us exactly what we need right now,” she said.

Tom Harter, who attended the Burlington, Iowa, speech with his 90-year-old mother, said there was something “calming” about Biden’s takedown of Trump.

“He has a stature about him,” Harter said.

Trump also took notice of Biden’s speech, calling it boring. The president later lashed out at his Democratic Party critics, accusing them of bringing racism into the national discourse, and Republicans are reveling at Biden’s Thursday misstep.

Trump campaign operatives quickly circulated video of the remark, part of a 105-minute discussion with unions members, Latinos and Asian Americans, exposing Biden to heat from some progressives and the GOP.

Biden adviser Kate Bedingfield responded Friday, saying the former vice president clearly “misspoke and immediately corrected himself” as part of his routine assertion that “all children deserve a fair shot.” Trump, Bedingfield added, is “desperate to change the subject from his atrocious record of using racism to divide this country.”

Other Democratic candidates joined Biden this week in hammering Trump, who has bristled at any suggestion that his harsh, anti-immigrant rhetoric contributed to the shooting in El Paso. During visits Wednesday to El Paso and Dayton, Ohio, Trump repeatedly tangled with his adversaries, including presidential candidate and former Rep. Beto O’Rourke, an El Paso native.

O’Rourke and Sen. Cory Booker delivered high profile remarks following the shooting this week, with Booker choosing as his venue the Emanuel AME Church in Charleston, South Carolina, where a white supremacist in 2015 killed nine black citizens as they prayed. Both candidates trail Biden and several others in the 2020 Democratic field.

But even as Biden’s top competitors shred Trump, they have built their central campaign pitches around something else.

Sanders and Warren, in particular, are economic populists of the left. California Sen. Kamala Harris released her first paid ad this week centered mostly on voters’ economic concerns.

Iowa State Rep. Dennis Cohoon, who has endorsed Biden, said that while he believes the former vice president can compete on policy, his best argument to navigate the long campaign remains one aimed at the incumbent president.

“If you know Joe Biden,” Cohoon said, “you know he’s the right man for this moment.”