Even before his diagnosis, the President had taken to calling drug companies to check on their vaccine trials, asking how much longer they'll take and ginning up the pressure around his desire for a vaccine before Election Day. He's also signaling he might speed up the federal approval process, conspicuously stalling Food and Drug Administration recommendations that would delay a vaccine authorization.

In his conversations with major drug-makers working on coronavirus vaccines, Trump has been explicit in telling the companies' CEOs that he'd like to see a vaccine move quicker than some of his health advisers say is reasonable, according to a person familiar with the conversations. He has asked whether they believe they can speed up their timelines and has suggested he is concerned that the FDA's regulatory process could slow down progress.

Trump's repeated calls -- especially to Pfizer, whose progress the President sounds most hopeful about recently -- are likely to continue through a presidential election that may turn on how voters perceive his handling of the public health crisis.

Meantime, experts worry what Trump's undivided attention means for the fate of the vaccine. With so much obvious political pressure coming to bear, people may fear that the vaccines aren't safe for widespread use. Beyond that, they may lose trust in federal regulators and, possibly, in research science.