Theresa May
President Donald Trump and British Prime Minister Theresa May (L) participate in a joint press conference at the East Room of the White House, Washington, D.C. Jan. 27, 2017. Getty Images/Alex Wong

While the 2017 elections in the United Kingdom on Thursday will decide the fate of the British economy in the coming years, it is also going to decide the kind of relationship the country ends up having with the United States, which is one of its biggest allies.

The U.S.-U.K. relationship has been fairly constant over the years with a few minor hiccups down the road. While the early part of 19th century saw turbulence between the two nations, the issues were quickly resolved and both the countries repaired diplomatic relations post-1815.

“Relations were strengthened by the United Kingdom’s alliance with the United States during both World Wars, in the Korean conflict, in the Persian Gulf War, in Operation Iraqi Freedom, and in Afghanistan, as well as through its role as a founding member of the North Atlantic Treaty Organization (NATO),” says the website for the U.S. embassy in the U.K.

Read: Prime Minister Theresa May Says 'Enough is Enough' After Terrorist Attack In London

Changing leadership and governments in both the U.S. as well as the U.K. have played crucial role in determining what kind of relationship both countries shared at any given time.

The present British Prime Minister Theresa May, for instance, did not have the most cordial relationship with former President Barack Obama, disagreeing with many of his foreign policies, including his administration’s stance on Israel, the Washington Post reported.

Theresa May
Former President Barack Obama shakes hands with British Prime Minister Theresa May during a luncheon the sidelines of the 71st session of the United Nations General Assembly in New York, Sept. 20, 2016. Getty Images/JIM WATSON

On the other hand, while May had also criticized President Donald Trump’s harsh discourse on Muslims and women during his campaigning days, her stance changed once he became president. She was one of the first world leaders to congratulate him on winning the election.

"I would like to congratulate Donald Trump on being elected the next president of the United States, following a hard-fought campaign... I look forward to working with president-elect Donald Trump, building on these ties to ensure the security and prosperity of our nations in the years ahead,” she said, the Telegraph reported.

She also became the first world leader to visit Trump in Washington D.C. after his inauguration in January 2017. Over the period of Trump’s administration she has either defended the POTUS or dialled back the criticism of policies to a bare minimum. She did not question his travel ban or the fact the FBI is looking into possible collusions between members of Trump administration and Russia.

“Decisions about what President Trump discusses with anybody that he has in the White House is a matter for President Trump,” she said, The New Yorker reported.

Theresa May
President Donald Trump speaks with British Prime Minister Theresa May during a working dinner meeting at the NATO summit at the NATO headquarters, in Brussels, Belgium, May 25, 2017. Getty Images/Matt Dunham

At the same time, although Trump’s interactions with May’s opponent in the 2017 British elections and British Labour Party leader Jeremy Corbyn have been non-existent till now, if the tables are turned against May in this election, the POTUS could face a challenge working with Corbyn.

Environmentalism is one of the key agendas being pushed by Corbyn’s party and he has not held back when it comes to rebuking Trump for withdrawing from the Paris climate accord, BuzzFeed reported.

Corbyn said a government should be one that “measures its success by improvements in our natural world and the sustainability of our environment. A Labour government wouldn’t hesitate to ring up and write to Donald Trump to say 'Sorry, mate, you’re wrong—stand by the Paris agreement.'"

"It is very, very difficult to imagine Trump and Jeremy Corbyn getting on," said Timothy Bale, a professor of politics at Queen Mary University of London, USA Today reported. "They are somewhat similar in age, I guess we can say that (Trump is two years older), and so maybe they like the same kind of music?"

 Jeremy Corbyn
Labour Party Leader Jeremy Corbyn arrives prior to the launch of the Labour Party Election Manifesto, at Bradford University in Bradford, England, May 16, 2017. Getty Images/Leon Neal

Meanwhile, some of the poll numbers are showing the gap between the Conservative Party and the Labour Party is closing up, with one of them even suggesting it dropped to just a point, Straits Times reported. The easy victory that May’s party was looking forward to, might not happen.

This leaves the road wide open for the diplomatic relations between the U.S. and the U.K. to swing either way, with one leader determined to make things work with Trump and another, not hesitant to challenge him.