Within days of former President Donald J. Trump vilifying immigrants on national television with false stories about Haitian migrants eating pet dogs and cats in an Ohio town, someone began threatening to blow up schools, City Hall and other public buildings, forcing evacuations and prompting a wave of fear.

Days later, authorities said, a man who described himself online as a disaffected former Trump supporter made his way with a semiautomatic rifle to the former president’s Florida golf course, evidently looking to take a shot. He was thwarted only when an observant Secret Service agent spotted him and opened fire first.

And so it goes in 2024. In the space of less than a week, the once and possibly future commander in chief was both a seeming inspiration and an apparent target of the political violence that has increasingly come to shape American politics in the modern era. Bomb threats and attempted assassinations now have become part of the landscape, shocking and horrific, yet not so much that they have forced any real national reckoning.

“One of the things I’m most concerned about right now is the normalization of political violence in our political system. It’s on the increase,” Representative Jason Crow, Democrat of Colorado and a member of a bipartisan task force already investigating the July 13 assassination attempt against Mr. Trump, said in an interview. “Now we’re on the second one in as many months and it just shows the extent to which this has become pervasive.”

President Biden and Vice President Kamala Harris both issued statements condemning the latest incident, but the campaign continued uninterrupted. Barely four hours after Mr. Trump was hustled into a motorcade away from the golf club for his protection, his finance team sent out an email to its fund-raising list with a button to click to make a donation. “My resolve is only stronger after another attempt on my life!” Mr. Trump said in the email. Ms. Harris’s fund-raising emails continued as well.

Mr. Trump, who as recently as last week’s debate with Ms. Harris blamed Democrats for the shooting at a rally in Butler, Pa., that struck his ear in July, attributed Sunday’s attempt to the president and vice president as well, arguing that the arrested suspect was acting in response to their political attacks.

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