Boris Johnson won the race to become prime minister with a pledge to take on and defeat opposition Labour Party leader Jeremy Corbyn.

The two men come from very different political traditions, yet both are populists who relish the idea of facing each other.

Corbyn's supporters believe Johnson is a divisive figure who will energise Labour's metropolitan base.

However, Johnson believes Corbyn is an unreconstructed left-winger who can be easily beaten.

"I think it will be an interesting psephological experiment in what happens when a left populist goes up against a right populist," one ally of Corbyn tells Business Insider.

"The one thing Boris does is that he re-energises our base," one ally of Labour Party leader Jeremy Corbyn told Business Insider.

"He reminds our voters who the enemy is."

Boris Johnson's victory this week has certainly energised some people. Johnson's speech upon becoming prime minister could barely be heard on Downing Street above the sound of the large protests against him.

His commitments during the campaign to slash taxes for higher earners, and to force through a potential no-deal Brexit, appear to have inflamed what was an already committed opposition towards him.

Business Insider reported last month that the prospect of Johnson become the United Kingdom's next prime minister had led to anti-Brexit groups enjoying a significant increase in donations and support.

In Parliament too, he has been an energising presence.

His first appearance at the despatch as prime minister opposite Corbyn on Thursday was a notably noisy and lively affair after several years of often tedious and dull exchanges between the Labour leader and Theresa May.

Targeting Labour voters

Johnson's appointment as prime minister does worry some figures around Corbyn.

On the one hand, his role as the frontman for the Vote Leave campaign has made him public enemy number one among many younger, metropolitan, pro-European voters, who now make up the bulk of Labour's electoral base.

But on the other, some of those around Corbyn are concerned that he could be highly effective at targeting the smaller but still significant minority of Labour voters the party needs in order to win the next election.

The fear among some of those around Corbyn is that Johnson will hoover up disgruntled Labour voters who supported leaving the European Union and gain a honeymoon bounce, before triggering a general election.

"If you look at the Peterborough by-election and local elections, most of the Lib Dem surge there was just taking seats from the Tories and if we were to gain all of that Lib Dem vote back it wouldn't gain us any extra seats," one Labour source told Business Insider.

"But where we've lost our Leave voters, they're in two-way Tory seats."

Indeed, it was notable on Thursday that Johnson devoted much of his attacks against Corbyn in the House of Commons towards accusing him of wanting to stop Brexit.

"It's entirely possible that he will hoover up all our Leave voters and get a ten or twenty point lead in the first few months," the source added.

Battle of the populists

Jeremy Corbyn asks Boris Johnson questions in the House of Commons. Getty However, even if that does happen, Labour believes that Johnson, who was this week branded the "Britain Trump" by the US president, can ultimately be beaten.

"I think a Johnson versus Corbyn contest would excite the public actually," one ally of the Labour leader told Business Insider.

"It will be a proper left-winger versus a proper right-winger."

They predicted that in a general election Johnson, and his strongly right-wing cabinet, would help mobilise their own base against him, while bringing back worried former Labour voters who have previously defected to the Lib Dems.

"I think it will be an interesting psephological experiment in what happens when a left populist goes up against a right populist," they predicted.

And with many observers expecting that Johnson is preparing for an autumn election, we may not have to wait very long to see how that experiment ends.