According to a leaked poll, Mr Trump was down 16 points in Pennsylvania, a key swing state

Donald Trump has instructed close advisers to play down internal White House polling that showed him losing heavily to Joe Biden in key industrial "rust belt" states ahead of the 2020 election.

According to a leaked 17-state poll, conducted by the president's pollster Tony Fabrizio, Mr Trump was down 16 points in Pennsylvania, and 10 points in Wisconsin, both of which he won narrowly in 2016.

Mr Trump was also trailing Mr Biden by seven points in Florida, which he won in 2016, and was only two points ahead in the traditionally Republican state of Texas.

As Washington was gripped by its first bout of 2020 poll fever White House officials said their own initial research no longer carried any weight.

In a statement Brad Parscale, Mr Trump's campaign manager, said the polling was "ancient," having been conducted in March.

That was before the release of the Mueller report, which found no collusion between the campaign and Russia, and prior to Democrat candidates revealing their "far-left policy message," he said.

Mr Parscale added: "Since then we have seen huge swings in the president’s favour across the 17 states we have polled."

However, public polls released this week also showed what even Republican strategists described as "warning signs". The first national poll of the campaign by Quinnipiac University showed Mr Trump trailing by 13 points in a hypothetical race against Mr Biden, should he become the Democrat presidential nominee.

Joe Biden thinks he has the credentials to win back voters in the Rust Belt states Credit: Bloomberg

Mr Trump was also down nine points to Bernie Sanders, eight to Kamala Harris, and seven to Elizabeth Warren. Pete Buttigieg and Cory Booker both led the president by five points.

"It’s a long 17 months to election day but Joe Biden is ahead by landslide proportions," said Tim Malloy, assistant director of the Quinnipiac poll. A separate Morning Consult national poll showed Mr Biden with a similar 11 point lead over Mr Trump.

In the rust belt state of Michigan a local poll also showed Mr Biden 11 points ahead. A University of Texas survey showed Mr Biden beating Mr Trump by four points in that state. And other polls showed Mr Trump trailing Mr Biden in Arizona and Iowa, which the president won easily in 2016.

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"If your Donald Trump's advisers you have to be concerned," said Larry Sabato, professor of politics at the University of Virginia. "This is a golden economy at the moment, it will never get better, and there may be some deterioration in it next year. If you're not winning in a golden economy that's a worry.

"All these recent polls have varying degrees of bad news for Trump, but it's early. Trump fears Biden because Biden makes most sense for the Democrats. But we also don't know whether Biden will throw it with a series of gaffes."

Sources briefed on the Trump polling from March say he was also down in Michigan, NV, MN (where his campaign had made overtures) and, more significantly, Georgia. Campaign has issued new statement from @TonyFabrizioGOP saying this data was "worst-case scenario" turnout model. — Maggie Haberman (@maggieNYT) June 14, 2019

Prof Sabato said recent polls in key states could "absolutely" be wrong, adding: "After 2016 I'll never believe the polls in Wisconsin again." If Mr Biden is ahead in the "rust belt" states like Pennsylvania, Wisconsin and Michigan, it opens up the possibility Mr Trump could take a different path to the White House in 2020.

That would mean winning other states where he came close in 2016, including New Mexico, Nevada, New Hampshire, Minnesota, Colorado, and Maine.

Campaign staff have already been dispatched to Nevada and New Hampshire, which a Republican has not won for two decades.

And Mike Pence, the vice president, has already been sent repeatedly to the southern state of Virginia, which Mr Trump lost by only five points to Hillary Clinton in 2016.

Mrs Clinton had an advantage then because her running mate was the Virginia senator Tim Kaine. Among the good news for Mr Trump in his private polling has been a rise in support among Hispanic voters in New Mexico and Nevada.

The president said polls showing him losing were "phony". He said there were "polls that we have that nobody saw" and "there's no way Biden beats me in Texas."

Nate Silver, the prominent election statistician, indicated much could change over time. He said: "Empirically, the margin of error on general election polls conducted this far out is around 25 points."