Sources are pushing back against President Donald Trump's claims that he spoke to one of his predecessors about the war against Iran.
Nancy Bush Ellis was an environmentalist who switched parties when her brother ran for president in 1979.
The three most recent former presidents hope an awareness campaign to promote confidence in its safety and effectiveness would be a powerful message.
Bush, who also served as Texas governor, called Biden "a good man, who has won his opportunity to lead and unify our country."
He did not refer specifically toward Trump, but he called the harassment toward African American protesters "a shocking failure."
"Let us remember how small our differences are in the face of this shared threat," the former president said.