Republican presidential nominee and former U.S. President Donald Trump arrives during the second day of the Republican National Convention at Fiserv Forum in Milwaukee, Wisconsin., Tuesday (local time). AFP-Yonhap

Former U.S. President Donald Trump's possible return to the White House is believed to be affecting the value of listed Korean firms on the benchmark KOSPI.

The Republican presidential candidate survived an attempted assassination during a rally, Sunday (KST), increasing his already considerable lead over incumbent President Joe Biden.

Against this backdrop, defense stocks on the KOSPI have been rising as Trump has been stoking geopolitical tensions. For instance, he says that the U.S. should leave NATO and is skeptical about continuing to provide aid to Ukraine in its ongoing fight against Russian forces.

Nuclear energy stocks also have been on the up as Trump backs advanced nuclear reactors in the middle of a global shift away from fossil fuel energy.

Trump, on the other hand, has called clean energy "a scam." Accordingly, secondary battery makers and other companies in the eco-friendly business have been retreating.

While it slid on Wednesday, the KOSPI had posted modest growth for the next two days after the attempted assassination of Trump. It gained 0.14 percent to close at 2,860.92 points, Monday, and also advanced 0.18 percent to finish at 2,866.09 points, Tuesday.

The pace of growth was much higher for defense stocks over Monday and Tuesday.

Over the cited periods, Hanwha Systems, an aerospace and defense arm of Hanwha Group, went up 5.62 percent and then another 4.24 percent.

Also a defense unit of the conglomerate, Hanwha Aerospace advanced 4.53 percent and again 1.69 percent.

Another industry peer, LIG Nex1, experienced a whopping 13.3 percent increase, Monday, although its pace of growth slowed to 2.56 percent the next day.

"The leading defense companies, including Hanwha Aerospace and LIG Nex1, have been securing more deals abroad recently, and Trump's possible return to the presidency can improve business prospects and further push up their stock prices," Hana Securities said.

Concerning the nuclear energy sector, Doosan Enerbility climbed 3.34 percent, Monday.

While it lost 2.77 percent, Tuesday, market observers said it is still considered a beneficiary of the "Trump effect" as it is a part of a Korean consortium involved in a 30 trillion won nuclear power plant project bid for the Czech Republic.

Other companies in the consortium include Daewoo E&C, which jumped 6.76 percent, Monday. It slid 3.75 percent the next day.

The European country will announce a preferred bidder possibly within this week.

"Being selected as a preferred bidder means higher chances for stock prices of the companies to move up," a market observer said.

In the eco-friendly industries, however, secondary battery maker LG Energy Solution lost 3.88 percent, Monday, and then another 3.34 percent, Tuesday.

A solar energy supplier, HD Energy Solutions fared well, Monday, as it only dropped 0.37 percent. On Tuesday, it slid 5.83 percent.