OTTUMWA, Iowa — President Trump and former Vice President Joseph R. Biden Jr. both traveled to the key early voting state of Iowa on Tuesday, trading attacks in sharply personal terms and giving the country a preview of what a general election matchup between the two men might look like.

Mr. Biden, who leads in early polls for the Democratic presidential nomination, described Mr. Trump as “an existential threat” who could fundamentally change the nature of the country and its values, and who is already jeopardizing America’s standing around the world, remarks that came during an afternoon appearance at an events center here.

 

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Mr. Trump, as he departed the Oval Office, told reporters that he thought Mr. Biden was “a loser” and questioned his mental fitness. “I’d rather run against, I think, Biden than anybody,” he said. “I think he’s the weakest mentally, and I like running against people that are weak mentally. I think Joe is the weakest up here. The other ones have much more energy.”

The hostile exchange underscored the extent to which the two men are already waging a battle against one another. Mr. Biden has largely ignored his Democratic rivals while building his campaign around the urgent need to oust Mr. Trump. The president, mindful of polling that shows him trailing Mr. Biden in several key states, has targeted him in particular with ridicule.

Source: A ‘Loser.’ An ‘Existential Threat.’ Trump and Biden Trade Barbs as They Travel to Iowa