Here’s one thing Trump can do at his press conference to derail stocks, according to Jim Cramer

Donald Trump could send stocks tumbling at his press conference on Wednesday if his message centers around the repeal of Affordable Care Act, CNBC's Jim Cramer said Wednesday.

Stocks and Treasury yields have skyrocketed since Trump's Nov. 8 election victory amid the prospects of looser regulations in certain sectors, lower tax rates and fiscal stimulus.

Cramer said before Trump's 11 a.m. ET news conference that investors could witness a plunge, however, if the president-elect pivots toward a goal of repealing Obamacare instead.

"I think if [Trump] says we're going to spend a lot of time talking about the repeal of Obamacare before we get to anything else, I think you'll see a downturn," Cramer said on "Squawk on the Street."

Since Trump's win, the president-elect has raised other concerns besides tax reform via Twitter, like American automakers sending jobs outside the United States and potential conflicts with Russia.

On Tuesday, Trump told The New York Times he wanted Republicans in Congress to press for the immediate repeal of Obamacare and replace it "very quickly or simultaneously."