Stocks could drop 15% if Democrats sweep Capitol Hill: Billionaire Trump supporter Thomas Peterffy 

  • Wall Street would see a major correction if Republicans were to lose both of their Capitol Hill majorities, the Interactive Brokers founder says.
  • Thomas Peterffy says he'd be a buyer of stocks once the dust clears and the market bottoms.
  • If Republicans were to keep control of both the House and Senate in Tuesday's midterm election, he says he'd buy stocks right away.

Wall Street would see a major correction if Democrats were to take control of the House and Senate in Tuesday's midterm election, predicts Thomas Peterffy, founder of the Interactive Brokers online trading platform.

The stock market could drop as much as 15 percent if Republicans were to lose both of their majorities on Capitol Hill, the billionaire supporter of President Donald Trump said Tuesday on CNBC's Squawk Box."

"If the Senate also goes Democrat, then I think we could expect a 10 to 15 percent drop," Peterffy said.

A Democratic sweep in Tuesday's voting is seen as rather unlikely, according to polls and forecasters.

However, the most likely scenario is Democrats winning the House and Republicans keeping the Senate.

"I think on the short run that we'll have a negative impact on the market," said Peterffy of that outcome. He sees a divided House and Senate leading to a 2 to 3 percent pullback in stocks.

Under either outcome, Peterffy said he'd be a buyer of stocks once the dust clears and the market bottoms.

In the event of a Republicans sweep, also seen as unlikely, Peterffy said he'd buy stocks right away. "If both houses of Congress are retained by the Republicans, then I think we'll go back to the highs."

Democrats need a net gain of at least 23 House seats to wrest control from the GOP. The current balance of power in the 435-member House is 235 Republicans, 193 Democrats, no independents and seven vacancies.

On the U.S. Senate side, Republicans hold a slim majority of 51-49 seats.

"I think it all depends on tonight," Peterffy cautioned. "So, I am waiting."

Last month, the Interactive Brokers CEO had said he was considering changing his bearish views on the market.

Peterffy, who had turned negative on stocks in June, told CNBC on Oct. 11 that his firm's customers at the time had more than $50 billion of idle cash in their accounts, calling it a historic high.

WATCH full interview with Peterffy who denounces socialism

Sign Up for Our Newsletter Morning Squawk

CNBC's before the bell news roundup
Get this delivered to your inbox, and more info about about our products and services.
By signing up for newsletters, you are agreeing to our Terms of Use and Privacy Policy.