One of the women, Juanita Broaddrick, accuses ex-president Bill Clinton of a 1978 attack.
The event came shortly before Trump's Sunday night town hall-style debate against Hillary Clinton. The Trump campaign has been in turmoil since Friday's release of a 2005 recording in which the NewYork real estate tycoon speaks lewdly of grabbing women "by the pussy."
"Mr Trump may have said some bad words, but Bill Clinton raped me, and Hillary Clinton threatened me," Broaddrick alleged. "I don't think there's any comparison."
A fourth woman at the Trump event was a 12-year-old rape victim in the 1970s whose accused attacker was represented by Hillary Clinton, who was a young defense attorney at the time.
- DPA