US President Donald Trump has traded insults with his leading Democratic opponent, Joe Biden.
US President Donald Trump called his leading Democratic opponent Joe Biden a "dummy" Tuesday as they both turned to the battleground state of Iowa to deliver dueling speeches seen as previews of the bitter 2020 presidential election.
Leaving the White House for Iowa, Trump unloaded on Biden, a longtime member of Congress and former vice president under Barack Obama, branding him "weak mentally."
Minutes later, Biden used a speech in Iowa to describe Trump as "an existential threat to America."
According to Biden, 76, his presence in the midwestern state on the same day as Trump, 72, was a coincidence. But his speech amounted to a point-blank broadside against the president.
Far from championing American blue collar workers and farmers, as he repeatedly claims, Trump has made them "pawns" in tariff wars with countries ranging from rival China to close trading ally Mexico, Biden said.
"He thinks he's being tough. Well, it's easy to be tough when someone else is feeling the pain," Biden said of Trump.
"Trump may think Wall Street and the super rich built this country. They didn't.... The middle class built this country. The unions built the middle class," Biden said.
Trump, a real estate developer who has always burnished his image as a high-living tycoon, relies heavily on blue collar voters buying into his nationalist slogan of "America First."
In his trip to Iowa, the president was due to visit an ethanol plant to tout his backing for the biofuel, supplied by Iowa's politically important farmers. Later, he was addressing a Republican party dinner.
But even before hitting the road, Trump delivered a volley of zingers at his rival.
Mocking his past failed presidential runs, Trump called Biden a "loser" and appeared to feed a theory shared in rightwing circles that the former vice president is in poor health.
"He looks different than he used two, he acts different than he used to, he is even slower than he used to be," Trump said.
According to Trump, Biden and the nearly two dozen other Democrats vying for their party's nomination to seek the presidency next year, are the ones whose left-leaning economic and social policies are out of touch.
And far from regretting his bruising trade war strategy, the president is on something of a high after Mexico said it was agreeing to his demand for more action against migrants flocking to the United States in order to avoid threatened tariffs.
Celebrating the deal - although questions have been raised over how much of it recycles measures already agreed to months ago - Trump said his bigger tariffs war with China would be equally successful.
"Right now, China wants to make a deal very badly. It's me right now that is holding up the deal. And we are going to either do a great deal with China, or we are not doing a deal at all," he said.
"China ate our country alive during Obama and Biden."
Country for old men?
Trump officially kicks off his reelection campaign next week at a Florida rally.
In reality, he has never stopped campaigning since he entered the White House after a shock win over the widely predicted winner of the 2016 race, Hillary Clinton.
Backed by the incumbency and a booming economy, Trump should be a heavy favorite in 2020. But his presidency has so polarized the country and energized opponents that previous electoral patterns could be upended.
Biden, meanwhile, holds a strong lead in the Democratic nomination contest, but that is partly due to overwhelming name recognition - an advantage that will steadily erode.
He is also struggling to maintain his centrist platform when the most active section of the Democratic Party veers strongly to the left, boosting the likes of Elizabeth Warren and Bernie Sanders.
An issue facing both Trump and Biden is their age. Trump revels in boasting about his energy.
"I am a young, vibrant man," he said in April, baiting the slightly older Biden.
But Democratic candidates in their 40s and 50s - and even 37-year-old Pete Buttigieg - could yet seize the momentum and make their youth an issue in a country where many Democrats yearn for radical change.