For once, it’s what President Trump hasn’t tweeted that’s worrying Wall Street.

Stocks on Wednesday morning turned in their worst performance since September after reports surfaced that Trump tried in February to pressure then-FBI Director James Comey into dropping a probe into ex-national security adviser Mike Flynn.

While Trump regularly tweets responses to controversies in the early morning hours of the day after the event, the president’s official and personal Twitter accounts were quiet Wednesday morning.

The Dow Jones industrial average shed as much as 289.43 in morning trading, reaching a low of 20,690.32 before moderating a little. At 1 p.m., the Dow was off 254.18.

Traders were growing increasingly concerned throughout the morning after Trump didn’t take to Twitter to rebut Tuesday’s bombshell report that he asked Comey during a February meeting to stop the FBI investigation into his former adviser’s ties to Russia.

“I don’t know what that’s about. That looks a little interesting, doesn’t it? We’re always just one tweet away,” Chris Rupkey, chief financial officer at MUFG Union Bank, told The Post.

Traders were selling off stocks, fearful that the controversies would push back to next year Trump’s plan to stimulate the economy — including a massive tax cut, the beginning of a $1 trillion, multi-year infrastructure plan and a partial repeal of Dodd-Frank.

“The market may be waiting for the next shoe to drop,” Rupkey added.

The @POTUS Twitter account, which is sometimes used by Trump, only posted an announcement that he was giving a commencement address at the US Coast Guard Academy. During the speech, he made only general references to the media treating him unfairly, and didn’t address any specific stories.

While Rupkey predicted that the Dow could shed another 100 points, other traders were significantly more bearish.

One investor sent The Post a list of winners and losers for a “simple impeachment trade.”

Among those top positions: Buy gold, buy Treasury bonds, sell the S&P 500.

One other trade? Buy the Mexican peso.