The upcoming U.S. presidential election will almost certainly be a showdown between Hillary Clinton of the Democratic Party and Donald Trump of the Republican Party, as the two candidates have each all but clinched the nominations of their parties.

A former first lady, Clinton has already cleared the way to become the Democratic nominee. Her victories in four states last week gave her an almost unbeatable lead over runner-up Bernie Sanders in terms of the number of delegates.

Real estate mogul Donald Trump is also virtually assured of being the Republican nominee. He scored a major victory in Indiana on Tuesday, forcing Texas Sen. Ted Cruz, who has been chasing him, to end his campaign.

Cruz’s dropout prompted some Republican Party leaders to declare the New York billionaire to be the party’s presumptive nominee.

With the nominations of the two parties all but decided, attention now shifts to who will emerge as the winner in the November election, which is the first match-up between a male and a female candidate in U.S. presidential election history.

The Huffington Post reports in an article on its website that Clinton has a dominant lead in polls so far. It says the former secretary of state leads by as little as 3 percentage points and as much as 12 percentage points in 24 polls conducted in the U.S. since April 1.

Yet U.S. pollster Rasmussen Reports came up with a different survey result Monday. It reported that Trump’s approval rating hit 41 percent against Clinton’s 39 percent, the first time that the Republican candidate led the matchup since last October.

In another survey conducted a few days earlier, Rasmussen found the two candidates tied at 38 percent each. The polls suggest that Trump is gaining ground against Clinton in polling.

Trump’s ascension has put Seoul officials on alert, as the tough-talking non-establishment candidate has made controversial statements on many occasions that could jeopardize Korea’s security and economic ties with the United States.

On Wednesday, Trump reiterated his argument that the U.S. should be prepared to let allies defend themselves unless they pay more for American defense support.

During an interview with CNN, he asserted that South Korea should pay the entire cost of American troop presence in the country. “Why not 100 percent,” Trump said in response to an interviewer who noted that Seoul already pays about 50 percent of the cost.

Earlier, Trump said he would be willing to withdraw U.S. forces from South Korea and Japan if they did not substantially increase their contributions to the costs of stationing those troops.

The maverick candidate even suggested that South Korea and Japan be allowed to develop their own nuclear weapons in the face of growing nuclear and missile threats from North Korea.

Trump has also expressed negative views about the Korea-U.S. free trade agreement. Describing the deal as “bad and embarrassing,” he contended that it would further erode American manufacturing and kill more American jobs.

As Trump’s dangerous, ultra-nationalist rhetoric appears to resonate with a growing number of disgruntled U.S. voters, Seoul officials need to closely monitor the electoral trends in the U.S. They also need to prepare for a Trump presidency by building networks with the candidate and his advisers.