Blackstone’s Byron Wien predicts that stock-market investors are in for what could be a rude awakening, when Democrats retake the U.S. Senate in the coming 2020 elections.

I think the Democrats take the Senate. Enough information [will be] revealed in the proceedings to cause some of his supporters, as well as many independents, to throw their support to liberal candidates in 2020 state races

The prognostication is one of 10 events that will take markets by surprise in 2020, which Blackstone published Monday. Data show that flipping the Senate would indeed by a surprise to many. Analytics platform PredictIt shows investors placing a 72% probability that the Republicans maintain control of the upper house of Congress, and veteran political observer Larry Sabato also sees a Democratic takeover as unlikely.

He forecasts Democrats taking 46 seats in the chamber and Republicans winning 51, with 3 races in North Carolina, Arizona and Colorado as “toss-ups.” Even a Democratic sweep of those races, would cause the party to fall two short of control if President Trump wins reelection — as the Vice President casts the tie breaking vote in the Senate — or one short if Democrats are able to retake the White House.

Control of the Senate could have important implications for markets, especially if Republicans lose the White House as well. Democratic presidential candidates have proposed an array of policies including higher taxes on corporate profits, higher taxes on wealth and tighter environmental and financial regulations that could weigh on equity valuations.

Stock investors have cheered President Trump’s major achievement of corporate-tax reduction, and many have also lauded the administration’s efforts to lessen regulations on U.S. industries. The S&P 500 index SPX, -0.24%  has gained nearly 52% since President Trump won the 2016 presidential election.