The Democratic National Committee said in a statement that it contracted Mr. Creamer in June 2016 to do counterprogramming in cities where the Trump campaign was holding events. While the committee said it opposed the incitement of violence of any kind, it was also investigating any potential illegal activity by Mr. O’Keefe.

“The practices described in the video by this temporary regional subcontractor do not in any way comport with our longstanding policies on organizing events, and those statements and sentiments do not represent the values that the committee holds dear,” Donna Brazile, the interim chairwoman of the D.N.C., said in a statement. “We do not believe, or have any evidence to suggest, that the activities articulated in the video actually occurred.”

Mr. Creamer, who was portrayed by the narrator in the video as the “diabolical” mastermind of a team of Democratic consultants, said that Mr. Foval was no longer working with him and that he was stepping away from the campaign to avoid being a distraction.

“We regret the unprofessional and careless hypothetical conversations that were captured on hidden cameras of a temporary regional contractor for our firm, and he is no longer working with us,” said Mr. Creamer, who is not seen on tape endorsing the plans to create chaos. “While none of the schemes described in the conversations ever took place, these conversations do not at all reflect the values of Democracy Partners.”

Mr. Foval could not be reached for comment.

The Clinton campaign denounced the tactics discussed in the video while expressing doubts about the measures employed by Mr. O’Keefe.