(New throughout, updates prices, market activity and comments to market close)
By Stephen Culp
NEW YORK, Sept 29 (Reuters) - Wall Street closed lower on Tuesday, snapping a three-day winning streak as investors took money off the table hours before the first U.S. presidential debate.
All three major U.S. stock indexes lost ground.
"Tonight's presidential debate has the potential to move markets and investors are unlikely to take a large position in front of that," said David Carter, chief investment officer at Lenox Wealth Advisors in New York. "Right now, markets are clearly driven by events in Washington, bed it fiscal stimulus or the presidential election."
Market participants eyed the first head-to-head showdown between Republican President Donald Trump and Democratic challenger Joe Biden in a debate expected to air from Cleveland Tuesday evening.
The latest poll shows Biden leading nationally and in a number of battleground states.
While the election has implications for different sectors, notably healthcare, green energy and beneficiaries of Trump's corporate tax cuts, Goldman Sachs analysts expected a Democratic sweep of the White House and both chambers of Congress would be beneficial to S&P 500 profits through 2024.
"We think markets can do fine with either Trump or Biden, but they need to know who the winner is," Carter added. "But concern is rising about having a clear election winner in November due partly to so many mail-in ballots, which will take time to count."
In the closing days of September and the second quarter, the major indexes were on track for their first monthly declines since March, when mandated shutdowns slammed the economy.
Despite September's expected loss, the S&P and the Nasdaq were on course for their best two-quarter winning streaks since 2009 and 2000, respectively.
U.S. House of Representatives Speaker Nancy Pelosi unveiled a new, $2.2 trillion coronavirus relief bill proposed by House Democrats, a sign of potential progress in the partisan tug-of-war over the new aid package nearly two months after emergency unemployment benefits expired for millions.
Stocks were given a brief boost early in the session by data from the Conference Board, which showed consumer confidence surging past expectations this month with the largest point gain in 17 years.
Unofficially, the Dow Jones Industrial Average fell 133.7 points, or 0.48%, to 27,450.36, the S&P 500 lost 16.27 points, or 0.49%, to 3,335.33 and the Nasdaq Composite dropped 32.28 points, or 0.29%, to 11,085.25.
Among 11 major sectors in the S&P 500, energy and financials suffered the largest percentage losses.
Shares of Sorrento Therapeutics jumped after the company's COVID-19 antibody candidates showed promise in a study.
Fitbit Inc advanced after Reuters reported Alphabet Inc was poised to win EU approval for its $2.1 billion acquisition of the fitness tracker maker. (Reporting by Stephen Culp; Editing by David Gregorio)