Joe Biden and Kamala Harris both warned Americans this holiday weekend to be skeptical of anything Trump says about a potential coronavirus vaccine, saying they’ll take their cues from scientists and not the president.

Why it matters: The Democratic ticket is trying to strike the right balance — they want to warn that Trump may be making premature claims for political gain, but they don’t want t0 dissuade Americans from actually using a vaccine once one is safe and available.

• At an AFL-CIO virtual town hall, Biden said he would take a vaccine only if Trump had been “completely transparent and other experts in the country could look at it.”

Driving the news: Trump is attacking Biden and Harris for expressing concern that the president might accelerate the introduction of a vaccine for political reason.

• On Monday, Trump called on his opponents  to “immediately apologize for the reckless anti-vaccine rhetoric that they’re talking right now.”

Between the lines. Trump continues to hint that there could be a vaccine before the November election. At a press conference in New Jersey he teased that there could be a “very big surprise coming up.”

• Both Biden and Harris want to project optimism about the prospects for a vaccine, without creating an echo chamber for Trump's enthusiasm.
• “If I could get a vaccine tomorrow I’d do it,” Biden said earlier today . “If it cost me the election I’d do it. We need a vaccine and we need it now.”
• On Sunday, Harris told CNN: “I would not trust Donald Trump and it would have to be a credible source of information that talks about the efficacy and the reliability of whatever he’s talking about.”