Mr. Weaver, 61, is a longtime Republican presidential marketing campaign adviser who gained prominence throughout John McCain’s run in 2008 and in addition labored for John Kasich in 2016. The Instances reported last month, based mostly on interviews with 21 younger males, that Mr. Weaver had for years despatched unsolicited and sexually provocative messages on-line. The youngest particular person The Instances interviewed was 14 when Mr. Weaver first contacted him; the messages turned overtly sexual after he turned 18.

On Thursday, The Associated Press and New York magazine, citing unidentified former workers, reported that Lincoln Venture leaders knew about Mr. Weaver’s habits final summer time, which Mr. Schmidt has continued to disclaim. Mr. Weaver took a medical depart from the group in August and introduced final month that he wouldn’t return.

In its statement on Thursday night time, the Lincoln Venture stated that Mr. Weaver had “betrayed all of us” and referred to as accounts of his harassment of younger males “heartbreaking.” It stated that Mr. Weaver’s conduct “have to be reckoned with,” and stated it was bringing in “a best-in-class outdoors skilled” to “set up each accountability and greatest practices going ahead for The Lincoln Venture.”

The previous workers, of their letter, expressed anger that Lincoln Venture leaders had characterised stories concerning the group’s dealing with of Mr. Weaver’s habits as hit jobs from supporters of former President Donald J. Trump.

Insinuating that their efforts constituted a right-wing assault, they wrote, “is just not consistent with the values we signed as much as uphold, and resembles the techniques and habits we joined the Lincoln Venture to defeat.”

Over the past 12 months, the Lincoln Venture established itself because the main Republican group against Mr. Trump, skewering him with mocking advertisements and drawing a big following on the left. However for the reason that election, the group has been splintering. Two former board members, Ron Steslow and Mike Madrid, left in December. George T. Conway III, one other key determine within the group, has additionally departed.

Ms. Horn stated in her statement, “When The New York Instances report on Weaver got here out lately, I began getting cellphone calls from some victims who shared very disturbing tales about their interactions with him — interactions that apparently began almost a 12 months in the past and, in response to these younger males, had been communicated to others within the Lincoln Venture.”