Reade has accused Biden of sexually assaulting her when she was an employee of his Senate office in 1993.
The Biden campaign said the presiden't son was trying to distract voters from the administration’s handling of the coronavirus.
Campaigners are warning that the US serves as a warning of how lobbyists could try to undermine the NHS.
"Fire in the hole," Trump campaign manager Brad Parscale tweeted as he released the ad.
Reade says she filed a complaint about sexual harassment in Biden’s office in 1993, but "did not complain formally" about the alleged assault. Biden flatly denies wrongdoing.
Biden went on "Morning Joe" and denied the allegation "unequivocally".
The Sanders campaign was mocked, ridiculed and maligned. But five years after it first started, it's clear it has altered the country's trajectory.
"I cannot in good conscience continue to mount a campaign that cannot win," Sanders said Wednesday.
If Sanders drops out, he'll forfeit his unique power to influence the Democratic Party's coronavirus response.
Florida and Illinois are two of three states that decided to continue its primary elections Tuesday in spite of the threat of coronavirus.
A majority of Democratic primary voters have, at least for now, lined up behind Biden. And barring a huge shakeup, it’s hard to see how Sanders catches him.
The result could prove devastating for Sanders, who has been banking on a big primary win in the blue-collar state to reverse his fortunes.