Priorities USA Action, the main “super PAC” supporting Hillary Clinton, raised $8.6 million in April, the group said on Friday, bringing the total it has raised to more than $76 million.

The group has about $47 million on hand, much of which will be used to savage Donald J. Trump, the presumptive Republican nominee, with negative ads that will not stop until Election Day.

The prospect of a grueling campaign against Mr. Trump has helped the group break its fund-raising records and bring in more money than it did in 2012 to help President Obama win re-election against Mitt Romney. Donors have pledged an additional $45 million in future donations, signaling that the race to defeat Mr. Trump will continue to be exceedingly well funded.

The group started running ads this week in Ohio, Florida, Virginia and Nevada, which attempt to use Mr. Trump’s previous statements about women against him. But Guy Cecil, the group’s chief strategist, has said it plans to expand its lines of attack to Mr. Trump’s business record, in an effort to portray him as out of touch with the working-class Americans who form a large base of his support.