Ackman, who runs Pershing Square, said that he thought having a businessman as president could be a big plus. And he said he thought Trump could get something positive done.

“He’s going to launch an infrastructure program. He’s going to take corporate taxes down to sensible levels. He’s going to get things done,” said Ackman on Thursday, speaking at the New York Times annual Dealbook conference. “And that’s extremely bullish for growth in the United States.”

Ackman said he thought progress in Washington would likely make CEOs more optimistic and likely to make new investments. And that’s why the stock market has rallied since Trump won the election, he said.

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One of Wall Street’s best known hedge fund managers, Ackman is noteworthy for being a so-called activist investment style, which entails taking positions in companies and pushing for changes. But he’s also been one of the worst performing among those managers as of late. Ackman’s Pershing Square fund was down 20% last year.

And 2016 hasn’t been any better either. The fund is down 20.7% this year, through the first eight days of November. Shares of Valeant Pharmaceutical (VRX), one of Ackman’s largest stock holdings and where he is a board member, have fallen 95% in the 12 months.

Ackman, however, says he hasn’t changed his investment portfolio since Trump has won the presidency.

What’s more, the full bore support of Trump is more evidence of another of Ackman’s bad predictions. A little over a year ago, Ackman predicted that Mike Bloomberg would end up running for President and that he would win.

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Ackman also acknowledged for the first time that he made a mistake on Herbalife, the diet shake maker that the hedge fund manager has publicly bet against. Earlier this year, the FTC fined the company but declined to call it a pyramid scheme. Ackman has called for the company to be shut down.

On Thursday, Ackman said Herbalife would be his last “public short,” where he bets against a company and then tries to make his case directly to other investors. Ackman said it has left him too vulnerable to other investors and public scrutiny.

“In the future I am going to bet against the stock and then deliver my material to John Oliver,” says Ackman, referring to the late night TV host who has also been critical of Herbalife. “He’s the greatest man ever.”