Another Circuit Breaker! U.S. Midterm Elections Stir Up Market Storm, Why Is the South Korean Stock Market the First to Be Hit?

The Democratic Party’s sweeping victory in both chambers of the U.S. midterm elections triggered concerns over tightened AI data center regulations, sending shockwaves through the seemingly calm markets and rippling swiftly to Seoul’s stock market. South Korea’s two benchmark indices simultaneously triggered sell-side circuit breakers, and leading semiconductor stocks took heavy blows—this "blue tsunami" is now testing Korea’s core export engine.

On November 5th, the Korea Composite Stock Price Index (KOSPI) fell 1.82% at the open, with losses deepening as the day continued. By late morning, the sell-sidecar mechanism was triggered, temporarily halting programmatic sell orders. As of 2:25 PM, KOSPI plummeted 5.50% from the previous session to 5,371.41 points, while the KOSDAQ fell 5.11% to 678.4 points. Both indices unusually activated market stability mechanisms on the same trading day. Shares of Samsung Electronics and SK Hynix dropped sharply by 7.8% and 9.81% respectively.

The immediate trigger for this plunge stemmed from market concerns that new data center approvals might be hindered, after the Democratic Party secured gubernatorial victories in data center strongholds like Texas, Ohio, and Georgia. Given Samsung Electronics and SK Hynix together account for more than half of KOSPI’s market capitalization, any fluctuation in semiconductor sentiment has an amplified impact on Korea’s benchmark index.

The Democratic Party achieved a historic "blue wave" in this midterm, gaining control of both the House and Senate, while also securing governorships in several states with high data center density.

In particular, Texas Governor-elect Gina Hinojosa pledged during her campaign to immediately halt all new data center approvals upon taking office. According to a DataCenterWatch analysis cited by the Texas Tribune, among 74 gubernatorial candidates in 36 states, 43% expressed support for pausing or banning new data center construction.

Market reactions were also directly influenced by the previous session’s U.S. market performance. Although major U.S. stock indices rose on the 4th—S&P 500 up 1.58%, Dow Jones up 3.03%, Nasdaq up 1.44%—sectoral divergence was pronounced.

Large technology stocks such as Apple, Microsoft, and Amazon each surged over 5% in a single day, while semiconductor names like Nvidia, Micron, SanDisk, and Intel all generally declined, with losses ranging from 3% to 8%. Emerging AI compute lessors CoreWeave and Nebius tumbled 9.9% and 6.7% respectively, while the Philadelphia Semiconductor Index dropped 3.1%, hitting a six-month low.

The plunge in the Korean market focused on the semiconductor and power equipment sectors closely tied to AI infrastructure. Samsung Electronics slid 5.39%; SK Square fell 6.56%; Samsung Electro-Mechanics dropped a staggering 10.31%. Semiconductor equipment makers on KOSDAQ also suffered heavy losses, with Jusung Engineering dropping 10.23%, Simmtech down 13.90%, and EO Technics off 11.72%.

Power equipment firms, such as transformer manufacturers, were also not spared. Market worries center on data center project delays directly shrinking transformer demand. Shares in Hyosung Heavy Industries, HD Hyundai Electric, and Sanil Electric slid 10.10%, 7.53%, and 12.84%, respectively.

Seo Sang-young, analyst at Mirae Asset Securities, noted, "The Democratic victory in key data center states like Texas and Georgia is heightening concerns over tightening grid access, approval processes, and power cost regulations. Heavily leveraged firms building new data centers will see higher financing costs and increased profit pressures if project timelines are delayed."

Kim Seok-hwan, Senior Research Fellow at Mirae Asset Securities, added, "Stricter AI regulation could disrupt the capital expenditure plans of big tech. These corporations must build data centers to honor compute commitments to clients such as OpenAI and Anthropic, and ultimately convert these into cloud revenue. Construction delays will push back revenue realization, prompting hyperscalers to reassess their investment pace, thereby pressuring demand forecasts for high-bandwidth memory and other advanced chips."

The Bank of Korea’s New York office noted in a report that the election results are unlikely to prompt a major shift in the overall policy direction of the Trump administration but "may have limited impact on AI regulation and related investment pace."

Yang Jun-seok, Economics Professor at the Catholic University of Korea, observed that even with Democratic control of both chambers, they may not secure the two-thirds majority required to override a presidential veto, fundamentally restricting their policy maneuvering room. As such, election results alone may not yield immediate, material impact on AI investment.

He further emphasized that should the Democratic Party clarify a tougher stance on AI development and investment—compounded by existing industry pressures such as public worries over AI’s impact on jobs, rising energy bills, massive water consumption, and the heavy debt loads of big tech investing in AI—these may evolve into "meaningful additional headwinds."

Meanwhile, Jo Yeon-ju of NH Investment & Securities maintains a more optimistic outlook: "The Democratic Party is also fully aware of the strategic importance of AI supremacy and would be unlikely to risk wholesale delays. Instead, they may favor providing local compensation to facilitate data center construction. The real impact on Big Tech could be just a tempest in a teapot."

An analyst from iM Securities also pointed out that while regulatory headwinds around AI data center approvals are dampening semiconductor investor sentiment, expectations of cost savings from falling oil prices are spreading to sectors like aviation and transport, meriting continued attention.

Amid broad market pressure, some sectors are seen as potential beneficiaries of the "blue tsunami." As Democrats consolidate their majority, expectations are rising for a revival of renewable energy support policies, making solar, wind, nuclear, and energy storage system (ESS)-related stocks widely viewed as potential winners.

DS Investment & Securities researcher Ahn Joo-won commented, "With the Democratic Party having an overwhelming legislative advantage going forward, demands from renewable energy sectors like solar and wind will be amply reflected in policy. Related stocks in wind and fuel cells will benefit."

Yuanta Securities analyst Lee Jae-won cautioned, "With Democratic control of Congress and key governorships, the likelihood of stricter AI data center regulation rises. Approvals and grid cost pressures in major data center locations such as Texas may slow AI capital investment processes, thereby suppressing memory chip demand and pricing."