Former Vice President Joe Biden on Wednesday excoriated President Donald Trump for a “toxic tongue” that he said has inflamed the nation’s divisions, saying that he lacked the moral authority to lead America.

Addressing voters in rural southeastern Iowa as the president traveled between two American cities reeling from mass shooting incidents, Biden drew a direct link between Trump’s rhetoric on immigration and what appeared to motivate the alleged shooter in Saturday's attack on El Paso, Texas. The shooter is said to have posted an anti-immigration screed online that Biden compared to Trump's past comments about immigrants.

“We have a problem with this rising tide of supremacy, white supremacy in America and we have a president who encourages and emboldens it,” Biden said. “His own FBI director recently testified to Congress that extreme white right-wing groups, white nationalists, pose the greatest threat to racially motivated domestic terrorism. And what has Trump done? He's poured fuel on the fire.”

Biden has long framed the 2020 election as a battle for the “soul of the nation,” a point he underscored again Wednesday. Biden said America has always been a nation in struggle between the ideals of its founding documents but the stain of slavery, racism and injustice. But time and time again, presidents have “stood against hate at moments when we were most tested.”

Over the course of a nearly half-hour address Biden named a slew of former presidents – from George Washington to George Bush, from Thomas Jefferson to Barack Obama. But he cast Trump as the aberration, saying he had “more in common with George Wallace than he does with George Washington.”

“Trump offers no moral leadership, seems to have no interest in unifying this nation. No evidence that the presidency has awakened his conscious in the least,” Biden said. “Indeed, we have a president with a toxic tongue who has publicly and unapologetically embraced the political strategy of hate, racism and division. So it's up to us.”

Biden’s remarks at an event in Burlington, Iowa, came as Trump visited El Paso and Dayton, Ohio, where another mass shooting occurred on Sunday. Twenty-two were killed in Saturday’s massacre at an El Paso Walmart and nearby shopping area by a gunman who allegedly had driven across Texas to target the largely Hispanic community, a senior law enforcement official told NBC News.

The FBI also said it was investigating whether the Dayton shooter was “exploring violent ideologies” before he murdered nine people at a downtown entertainment district.

Another Democratic presidential candidate, Sen. Cory Booker of New Jersey, gave a speech Wednesday morning at the site of the Charleston massacre in which he criticized Trump's comments about immigrants and people of color and condemned white supremacy and bigotry, which he said has led to the shootings. Booker also called for banning assault-type rifles, stiffening licensing requirements and requiring federal assessments of terrorism threats from white supremacists.

Warning that "people’s very lives are in the balance," Booker said that "we can't let these conversations devolve into the impotent simplicity of who is or isn't a racist, because if the answer to the question, ‘Do racism and white supremacy exist?’ is yes, then the real question isn't who is or isn't a racist, but who is and isn't doing something about it," according to excerpts provided to NBC News.

Trump condemned “racism, bigotry and white supremacy" in a televised address to the nation Monday after the shootings, saying, "These sinister ideologies must be defeated. Hate has no place in America."

The president did not specifically condemn anti-immigrant rhetoric on Monday, instead blaming violent video games and mental illness for the scourge of mass shootings that have been a steady drumbeat throughout his presidency. Trump also voiced support for stronger death penalty legislation for those who commit mass shootings, putting additional resources toward helping to identify early warning signs before shooters act, and reforming mental health laws.

Trump's campaign, in an emailed response to Biden's expected remarks, said, "It's a shame Joe Biden is sowing more division today, a day that should be about unity and support for Dayton, Ohio, and El Paso, Texas," before calling several of Biden's own past comments into question.

Trump appeared to be watching Biden’s address as he flew on Air Force One to El Paso, tweeting that his speech was “sooo boring.” Biden responded after his speech on Wednesday, telling reporters that the president should "get a life."

Watching Sleepy Joe Biden making a speech. Sooo Boring! The LameStream Media will die in the ratings and clicks with this guy. It will be over for them, not to mention the fact that our Country will do poorly with him. It will be one big crash, but at least China will be happy! — Donald J. Trump (@realDonaldTrump) August 7, 2019

White House press secretary Stephanie Grisham tweeted Tuesday night that Trump's visits on Wednesday would be "about honoring victims, comforting communities, and thanking first responders & medical professionals for their heroic actions."

The Biden campaign has long believed the former vice president’s candidacy is strongest in moments when the stakes of defeating Trump are highest. A Quinnipiac poll released Tuesday again showed that nearly half of Democrats believe Biden is the strongest candidate to face off with Trump in the general election, with a plurality of Democratic and Democratic-leaning independent voters saying they preferred a candidate who was electable to one that shares their views.

Biden also addressed what he called an epidemic of gun violence that is fueling “a literal carnage in America.” He cast himself as one of the few Democrats who has taken on the National Rifle Association and succeeded, primarily in securing a ban on the sale of certain types of assault weapons as part of the 1994 crime bill.

“We can't let this go on,” Biden said. “We can't and I will not let this man be re-elected President of the United States of America.”