Centrist Democrats are poised to argue that the routing of the Labour Party in Thursday's UK general election shows only someone like Joe Biden or Pete Buttigieg can beat President Donald Trump in 2020.

"Look what happens when the Labour Party moves so, so far to the left," Biden said on Thursday as the British election results became clear.

Backers of progressive candidates like Sens. Bernie Sanders or Elizabeth Warren, however, can point to distinct local factors that shaped the election result in the UK, most significantly Brexit.

Despite her winning popular vote by a big margin, progressives have also argued that Hillary Clinton's lackluster performance in 2016 in traditional Democratic states means they need something more radical.

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As news came in of the crushing defeat Thursday of Jeremy Corbyn's hard-left Labour Party in the UK general election, the US Democratic presidential candidate Joe Biden sought to draw a lesson for his own party in its quest to beat President Donald Trump in 2020.

"Boris Johnson is winning in a walk," he told journalists at a California fundraiser, according to a pool report, as results showed the British prime minister cruising to a historic victory.

He predicted that pundits would say: "Look what happens when the Labour Party moves so, so far to the left. It comes up with ideas that are not able to be contained in a rational basis quickly."

He also drew comparisons between Johnson — an outspoken former media star embraced by the populist right — and Trump.

US President Donald Trump and British Prime Minister Boris Johnson at a working breakfast in Biarritz, France, on August 25 on the second day of the annual G7 Summit. NICHOLAS KAMM/AFP/Getty Images

"You're also going to see people saying, my God, Boris Johnson, who is kind of a physical and emotional clone of the president, is able to win," Biden said.

As the 2020 election campaign gears up, debate is still heated between Democrats who want to pit Trump against a centrist such as the former vice president or Pete Buttigieg, the mayor of South Bend, Indiana, and those who want a left-winger.

At the same time, the progressive wing is convinced that Democrats needs to learn from the 2016 defeat of Hillary Clinton and choose a candidate like Bernie Sanders or Elizabeth Warren who can pledge radical reform.

Centrists will argue that, like the Labour Party in the UK, the policies of the left wing appeal mainly to young progressives and fail to persuade many of the party's traditional supporters or the swing voters necessary to claim victory.

Democrats like Biden and Clinton have traditionally found their closest UK allies in the Labour Party of former Prime Minister Tony Blair.

Blair was Labour's most successful postwar leader, but his successors, including Corbyn and his allies, accused him of selling out core Labour. They went on to demand a pivot to the left in a party civil war that mirrors that which the Democrats are now experiencing.

Trump and Republicans are seeking to frame the Democrats as extreme socialists in a relentless series of attacks via social-media ads and the president's Twitter feed.

And there are indications that the strategy is resonating with voters in some of the swing states that abandoned the Democrats to vote Trump into the White House.

Any further move to the left is ammunition for Republicans, centrists say, and risks the Democrats in 2020 being consigned to the same fate as Corbyn's Labour.

The Democratic presidential candidate Bernie Sanders at a fundraiser for the Nevada Democratic Party on November 17 in Las Vegas. Associated Press

But backers of Sanders and Warren could point to a range of differences they might argue make any comparison between the UK and the US meaningless.

The UK election, they will most likely say, was singularly defined by Brexit — an issue that has divided Britain since the 2016 referendum and one in which Corbyn's refusal to take a clear position appears to have cost him dearly at the ballot box.

In the US, they can argue, the political consensus is different from that in the UK.

Johnson's Conservative Party in fact moved leftward on issues such as healthcare and education in a successful bid to win seats in Labour's traditional heartlands.

On some issues, Tory policy is now more progressive than that of centrists like Biden, who oppose National Health Insurance-style state-funded healthcare.

Backers of Sanders can also argue that Trump's 2016 victory in Democratic-leaning swing states was an emphatic rejection of the centrism exemplified by Clinton.

There's evidence that a significant number of Sanders voters ended up voting for Trump in 2016. There are similar concerns that the Rust Belt states require a Democrat who is not vulnerable to the accusations of corruption and elitism that Trump successfully aimed at Clinton.

As we head into the new year and the primaries, one thing is for certain: Unlike in the UK election campaign, the battle for the soul of the Democratic Party is far from over.