The presidential hopefuls battled over abortion, the economy, immigration and Trump's legal woes at their combative first debate.

That left investors skittish in Asian trade as markets also geared up for US inflation data that could influence the Federal Reserve's policy moves next week.

The MSCI's broadest index of Asia-Pacific shares outside Japan dropped 0.25 percent, S&P 500 futures eased 0.38 percent, while the dollar was on the back foot.

Harris' late entry in the presidential race after President Joe Biden's withdrawal in July has tightened the race, prompting a reversal of trades that were put in place on expectations of a second Trump presidency.

While the debate is unlikely to sway near-term monetary policy, investors are focusing on fiscal policies and plans for the economy from the candidates.

"I don't think there's a lot for markets here," said Rob Carnell, ING's regional head of research for Asia-Pacific. "I think Harris seems to be managing Trump quite well."

"You'd expect if he [Trump] was doing better, that you'd see a strong dollar coming out of this. So I suppose that's the way the market is looking at it. It's a slight lean towards Harris."

The dollar index, which measures the US currency against six peers, was down 0.21 percent at 101.43 in Asian hours.

Japan's Nikkei fell 0.8 percent, while Chinese stocks eased again. The Shanghai Composite index was 0.75 percent lower while the blue-chip index fell 0.16 percent. Hong Kong's Hang Seng index slipped 1 percent.

Investor focus will soon switch to US Labor Department's consumer price index report later on Wednesday for policy clues although the Federal Reserve has made it clear employment has taken on a greater focus than inflation.

The headline CPI is expected to have risen 0.2 percent on a month-on-month basis in August, according to a Reuters poll, unchanged from the previous month.

While the Fed is widely expected to cut interest rates next week, the size of the rate cut is still up for debate, especially after a mixed labor report on Friday failed to provide clarity on which way the central bank could go.

"What we needed to see to spur the Fed into greater action would be much more obvious evidence of slowdown/recession, and in particular in the labor market. And I don't think we saw that the last payrolls report," said ING's Carnell.

Markets are currently pricing in 66 percent chance of the US central bank cutting rates by 25 basis points, while 34 percent chance is ascribed for a 50 bps cut when the Fed delivers its decision on Sept. 18, CME tool showed.

The dollar remained defensive, with the yen strengthening as much as 0.6 percent to 141.51 per dollar, highest since January, boosted by comments from Bank of Japan board member Junko Nakagawa.

Nakagawa reiterated in a speech that the central bank would continue to raise interest rates if the economy and inflation move in line with its forecasts.

In commodities, oil prices stabilized on Wednesday after dropping over 3 percent in the previous session, and still hovered near their lowest in three years after OPEC+ revised down its demand forecast for this year and 2025.

Brent crude futures was last 0.68 percent higher at $69.65 a barrel. US West Texas Intermediate (WTI) crude rose 0.75 percent to $66.25 a barrel.