Six 2020 Democratic presidential candidates would defeat President Donald Trump in a one-on-one general matchup, according to a new Quinnipiac University poll.

If the election were held today, former Vice President Joe Biden would beat Trump by a margin of 53 to 40%, while Vermont Sen. Bernie Sanders would beat Trump 51 to 40% and California Sen. Kamala Harris would come out ahead of Trump by 49 to 41%.

The poll found that Trump's national approval rating has slightly improved over the past month but is still underwater at 42% approval and 53% disapproval.

Trump and Biden have quickly become each other's biggest foes and ramped up the intensity of their public insults and jabs at each other.

The same day that Biden slammed Trump as "an existential threat to America" in an Iowa speech, Trump called Biden "a dummy," "mentally weak," and "1% Joe" in remarks to reporters.

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Six of the 24 declared 2020 Democratic presidential candidates would defeat President Donald Trump in a one-on-one general matchup if the election were held today, according to a national Quinnipiac University poll released on Tuesday.

The poll, which was conducted between June 6 and June 10 and surveyed 1,214 voters nationwide with a margin of error of plus or minus 3.5 percentage points, found:

Former Vice President Joe Biden beating Trump by a margin of 53 to 40%.

Vermont Sen. Bernie Sanders beat Trump 51 to 40%.

California Sen. Kamala Harris came out ahead of Trump by 49 to 41%.

Massachusetts Sen. Elizabeth Warren defeated Trump 49 to 42%.

Both New Jersey Sen. Cory Booker and South Bend, Indiana, Mayor Pete Buttigieg pulled ahead of Trump 47 to 42%.

The poll found that Trump's national approval rating has slightly improved over the past month but is still underwater at 42% approval and 53% disapproval.

"It's a long 17 months to Election Day, but Joe Biden is ahead by landslide proportions," the Quinnipiac pollster Tim Malloy said in a release announcing the poll.



"That said, the Trump bump to 42 percent job approval is nothing to sniff at. It's one point shy of the best Quinnipiac University survey number ever for President Trump," Malloy added.

Read more: Trump's approval rating is underwater in 8 major 2020 battleground states, and it's a troubling sign for his reelection prospects

Breaking down the demographics of Biden's head-to-head lead over Trump, Quinnipiac found that Biden comfortably leads among African American voters 85 to 12%, among female voters 60 to 34%, and among Hispanic voters by 58 to 33%.

Biden, however, leads by only a 1-percentage-point margin of 47 to 46% among both white and male voters.

While the general-election cycle won't begin for another year, and Biden isn't guaranteed to be the nominee, Trump and Biden have quickly become each other's biggest foes and ramped up the intensity of their public insults and jabs at each other.

This week, both are set to campaign in separate parts of Iowa. In a Tuesday speech in Davenport, Iowa, the text of which the campaign released ahead of time, Biden directly attacked Trump as "an existential threat to America" and slammed the effect his tariffs have on Iowa's farmers.

Read more: Trump slams Joe Biden as 'mentally weak,' calling him '1 percent Joe' and saying he's 'slower than he used to be'

While addressing reporters on the White House's South Lawn before departing on his own jaunt to Iowa, Trump called Biden "a dummy," "mentally weak," and "1% Joe" — a dig at Biden's poor past performances in the 1988 and 2008 Democratic primaries.

"I heard Biden, who is a loser — I mean, look, Joe never got more than 1%, except Obama took him off the trash heap," Trump said, adding that Biden would be his preferred opponent and that "he looks different than he used to, he acts different than he used to, he's even slower than he used to be."

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