President Joe Biden criticized what he said were efforts to restrict the teaching of US history, delivering a rebuke to Republican presidential challenger Ron DeSantis amid a brewing controversy over the Florida governor’s defense of the state’s educational curriculum.

“At a time when there are those who seek to ban books, bury history, we’re making clear — crystal, crystal clear — while darkness and denialism can hide much, they erase nothing,” Biden said at a White House event Tuesday establishing a national monument for Emmett Till, the Black teenager whose brutal lynching in 1955 galvanized the civil rights movement.

The event, on what would have been Till’s 82nd birthday, took place against a the backdrop of a heated controversy over the teaching of Black history. DeSantis has invited bipartisan criticism for defending a Florida state social studies curriculum that says formerly enslaved Black Americans gained beneficial life skills from chattel slavery.

Biden did not mention DeSantis by name but used the occasion to draw a contrast with one of his top 2024 rivals.

“We can’t just choose to learn what we want to know. We have to learn what we should know — we should know — about our country. We should know everything — the good, the bad, the truth of who we are as a nation,” Biden said.

For months, DeSantis has garnered criticism from the White House and Democrats for moving to curtail the teaching of Black history — a clash reignited by Florida’s new standards.

“They’re probably going to show that some of the folks that eventually parlayed, you know, being a blacksmith into doing things later in life,” DeSantis said Friday.

DeSantis has said he wasn’t involved in the curriculum but defended it after Kamala Harris, the first Black, Asian and woman US vice president, traveled to Jacksonville, Florida, on Friday to highlight the White House’s opposition.

Harris criticized those standards again Tuesday, without mentioning DeSantis by name.

“There are those in our nation who would prefer to erase or even rewrite the ugly parts of our past, those who attempt to teach that enslaved people benefited from slavery,” she said.

“Those who insult us in an attempt to gaslight us, who try to divide our nation with unnecessary debates,” Harris added. “Let us not be seduced into believing that somehow we will be better if we forget. We will be better if we remember.”

The flap comes at a delicate time for DeSantis, whose campaign is undergoing a reboot after a dismal start that has left donors anxious about his ability to supplant former President Donald Trump as the GOP standard-bearer. DeSantis has sought to outflank Trump, who is the Republican frontrunner by a wide margin according to polls, but remains firmly in second place.

Earlier: DeSantis to Shake Up Team Amid Campaign Spending Scrutiny

Some Republican presidential candidates have criticized DeSantis, including longshot contender Will Hurd, who said “implying that there is an upside to slavery is absolutely wrong,” in an interview Monday with Bloomberg Television’s “Balance of Power.”

Read more: Hurd Says DeSantis Wrong to Double Down on Slavery Curriculum

Tuesday’s event gave Biden an opportunity to shore up his ties with Black voters, a key part of the Democratic coalition that he largely credits with catapulting him to the White House. Biden carried 92% of the Black vote in 2020, but a July 18 The Economist/YouGov poll found his approval rating among those voters at just 64%.

The White House has cast DeSantis and other Republicans as extreme on issues including immigration, abortion and the teaching of critical race theory.

Biden’s campaign co-chair Cedric Richmond in a statement Saturday said DeSantis’s “comments in support of the idea that slavery had its benefits for slaves are obviously disgusting” and a sign of “extremism” among 2024 Republican candidates.

The proclamation Biden signed protects sites connected to the killing of Till and the efforts by his mother, Mamie Till-Mobley, to highlight his death. The proclamation follows a long-sought effort to honor Till’s legacy.

Biden last year signed legislation, named in honor of Till, that made lynching a federal hate crime. In February, he hosted a screening of the movie “Till,” about the life of Mamie Till-Mobley, at the White House.

Earlier: Biden to Host Screening of Film on Civil Rights Icon Till-Mobley

The monument spans three locations, including the Mississippi site where Till’s disfigured body was found, the church in Chicago where his mother held an open-casket funeral, and the courthouse where his killers were acquitted by an all-White jury.

--With assistance from Jenny Leonard and Justin Sink.