The pharmaceutical industry knows that Donald Trump’s war with them is fake.

This much became clear Monday morning, when the president attacked Merck chief executive Kenneth Frazier. Frazier quit the president’s council on manufacturing after Trump failed to “take a stand against intolerance and extremism” in Charlottesville this weekend.

Trump responded, characteristically, with a Twitter attack.

Now that Ken Frazier of Merck Pharma has resigned from President's Manufacturing Council,he will have more time to LOWER RIPOFF DRUG PRICES! — Donald J. Trump (@realDonaldTrump) August 14, 2017

Facing Twitter attacks from the commander in chief, large companies often see their stock prices tumble. The New York Times has shown, for example, that Ford took a significant hit when the president tweeted about the firm canceling a new plant.

But in the case of Merck, the exact opposite happened. Merck stock prices rose after the president’s harsh words.

As CNBC’s Carl Quintanilla noted, the pharmaceutical company has so far had its best day in weeks.

Wall Street knows that Trump’s tweet — raising the specter of a fight over drug prices — is a false threat. He has become the president who cried wolf on this particular topic.

During the campaign, Trump repeatedly discussed the idea of Medicare negotiating lower drug prices. “There's very little bidding on drugs,” Trump said at an event days before he took office. “We're the largest buyer of drugs in the world. And yet we don't bid properly. We're going to start bidding.”

This was an odd position for a Republican candidate to take; Democrats had typically been the party to advocate for government price controls in health care. But then again, Trump was an odd Republican candidate — and observers watched keenly to see if he would buck his party on this issue.

He didn’t. By every indication, Trump backed off of the idea after meeting with pharmaceutical executives a few weeks later. In the lengthy health care debate over repealing and replacing the Affordable Care Act, there is no indication that the White House pushed this idea as one that Republicans should pursue to help lower health care costs.

So investors seem to have shrugged off Trump’s attacks on Merck. They don’t read his tweet as a harbinger of policies that would regulate drug prices, but rather as a distraction. Merck’s president quit the manufacturing council and appears, by all accounts, to have come out unscathed. His company hasn’t suffered. Instead, they seem to be doing just fine — and Trump’s Twitter attacks aren’t having the power that they used to.