Investors ready for possible shake-up in Congress as Election Day arrives

By Lewis Krauskopf

NEW YORK, Nov 3 (Reuters) - Investors are weighing the market implications of a possible shift in control of US Congress in Tuesday's midterm elections, focused on whether a strong Democratic showing could pave the way for greater volatility in asset prices, particularly the AI trade which has been a main driver for markets.

The midterms come at a fragile time for markets, with a swoon in AI shares causing investor unease that could be exacerbated by the election results. Tuesday's outcome could hold broad implications for market-sensitive areas including the AI data-center buildout, the US fiscal outlook, defense spending, and regulation in areas such as healthcare, banking and cryptocurrencies.

President Donald Trump's Republican party has controlled both chambers of Congress during the first two years of his second term. Opinion polls show the Democrats are likely to take the House, while the Senate is too close to call.

"While probabilities increasingly favor a Blue sweep, several tightly contested Senate races leave open some possibility of Republican control of the Senate or, conversely, a greater than expected Democratic foothold in the Senate," Scott Chronert, US equity strategist at Citigroup, said in a research note. "Equity market reaction is likely positive in the former case and negative in the latter."

Strategists at UBS Global Wealth Management have assigned a 50% probability of a Democratic sweep, a 40% chance of Democrats winning the House while Republicans retain the Senate, and a 10% probability that Republicans hang onto both chambers.

"The most visible effects of a change in congressional control would likely be greater oversight of the administration and more difficult fiscal negotiations," Mark Haefele, chief investment officer at UBS Global Wealth Management, said in a note on Monday.

A Democratic-led Congress could exert greater scrutiny over AI companies, in part due to growing public opposition to data centers, a risk for a market that has been lifted by such investment spending. While analysts doubt any viable legislation would severely undermine the data-center buildout regardless of the election outcome, they expect a Democratic sweep to lead to investigations into the technology sector.

Many investors have said they are eager to get past the elections, which have hung over the markets for the last several weeks. Since 1970, in midterm election years, the S&P 500 index has gained in every six-month period following the election, according to Edward Jones.

While equity volatility has increased in recent sessions, option-market traders are nonetheless not bracing for a massive stock market move following the election results.

Options on the S&P 500 index are priced for a move of about 0.8% in either direction on Wednesday, slightly higher than the 0.6% average implied daily move over the past month, according to ORATS data.

"We could see some volatility come out once there is a clear result, but I wouldn’t assume all that uncertainty disappears Wednesday morning," said Joe Tigay, portfolio manager at Equity Armor Investments. "Election hedges can expire; geopolitical risk doesn’t have an expiration date."