How the US midterms could ripple through Australian markets, from renewables to AI stocks

On 3 November, Americans vote in midterm elections that Donald Trump is fighting to win control of Congress in, and the result will reach Australian markets whichever way it goes. Democrats need to flip four seats in both the House of Representatives and the Senate to overturn the narrow Republican majorities. Polls favour them to retake the House, while the Senate contest is too close to call.

Polling also suggests Republican chances of holding both chambers have faded as Americans struggle with high living costs, made worse by rising fuel prices. Even so, a Republican hold is the scenario analysts expect to produce the quickest market response: an immediate bump on Wall Street that would lift markets worldwide, Australia included. Rob Talevski, chief executive of Webull Securities Australia, says control of Congress would let Trump deliver signature fiscal stimulus, including a proposed US$5,000 payment to every adult American. He likens it to a Santa rally, a Christmas present for investors. But he expects it to be brief. "It would be short-term, and then the air would come out of the balloon," he says, as attention returned to high debt servicing levels, inflationary pressure and employment pressure. A Republican win would also reinforce Trump's pro-market stance and could revive a technology sector that has wobbled in recent weeks over fears of an AI bubble. Threats of shutdowns, budget standoffs and debt-ceiling negotiations would subside.

A split Congress, with Democrats holding the House and Republicans the Senate, would probably curb the administration's spending. Markets often welcome that, since less borrowing helps cool inflation. Anthony Malouf, an economist at Ebury, says a Democratic House would rein in fiscal expansion and ease the deficit anxieties that have weighed on markets in recent months. The catch is the debt ceiling, the legal limit on total federal borrowing. Gridlock would probably bring a bruising fight over it next year, which could rattle global equities and carries the potential for a US default, in which Washington says it can no longer pay its debts. Malouf calls the debt ceiling the biggest concern. Both parties face political risk in a stalemate, because voters can blame the opposition, and historically that has meant compromise. Major Democratic legislation would be unlikely, since Senate Republicans could block it. It is also unclear whether any change in Congress would affect the conflict with Iran, and with it oil prices, because Trump did not seek Congress's approval before strikes began.

A Democratic sweep would give the party more leverage over spending and debt-ceiling talks, though the risk of a protracted fiscal showdown would be high. It would not neutralise Trump's policies: he keeps his veto and can govern by executive order, which lets him hold positions such as tariffs and foreign policy. Democrats have promised to use a House majority to contest legislation, investigate the administration and challenge spending priorities. A Senate majority would add influence over judicial picks, ambassadors and other senior appointments.

Analysts expect a Democratic sweep to bring targeted pushes to boost renewable energy supply, increase battery production and restore EV incentives, all of which have waned under Trump. Australia is tied into that supply chain through its minerals sector, including lithium producers now suffering from depressed prices. Talevski says lithium could rebound if focus shifts back to batteries. Benchmark Mineral Intelligence says the US is an outlier among developed economies in seeing falling EV sales, though early signs suggest interest is turning around because of high petrol prices.

The tech sector could move the other way. Analysts at RBC Capital Markets say a sweep could drag it down, given clear signs of "AI angst" among voters that policymakers may respond to. That would weigh on US equities, but Australia's tech sector is modest and does not greatly steer the ASX. Malouf says a Republican hold could ignite a near-term boom, but a Democratic sweep might be more favourable over the longer term because of the prudence Democrats would likely bring in a hostile and uncertain time.

The outcome that could unsettle markets most is a contested result, with fights over ballot counts creating policy uncertainty. Prolonged uncertainty tends to weigh on commodities, one of the ASX's biggest sectors, because resource-using industries often pause development plans when policy is unclear. History offers mixed guidance, and most disputed results came in presidential rather than midterm elections. Trump did not concede in 2020 for months, yet markets quickly looked past the legal challenges once counts showed a clear winner. In 2000 the presidential result took five weeks, but it was the unravelling dot-com bubble that pushed markets lower, a dynamic that may resonate with investors wary of today's AI valuations. The Senate race, the debt-ceiling timeline and any recovery in renewables and lithium are the things to watch.