CONCORD — Third Congressional District candidate Rufus Gifford responded publicly in optimistic terms Monday to a since-deleted video criticizing him that circulated online over the weekend.

The attack ad spliced together segments from the documentary, “I Am the Ambassador,” produced by a Danish network when Gifford was the U.S. ambassador several years ago, to question the candidate’s connections in Massachusetts and how he would work as a politician.

Its origins are somewhat murky: the ad’s first appearance seems to be in a Dropbox link tweeted early Sunday morning by Jordan Markwith, a Democratic consultant in California. It was retweeted by former 3rd District candidate Steve Kerrigan — whose 2014 lieutenant governor campaign received donations from Markwith, state records show — but Kerrigan told The Sun he simply saw the tweet and shared it and was not involved in any other way.

The video, which was re-posted by other users, has since been taken down. According to the Gifford campaign, it violated Twitter’s terms by using copyrighted material from DR, the Danish broadcasting company who produced the documentary. (Neither Twitter nor DR could be reached Monday for confirmation.)

In a YouTube video posted Monday morning titled “Positivity Pledge,” Gifford pushed back against the video, describing it as an intentional distortion of his words. He said his efforts on the campaign trail would remain positive through the Sept. 4 primary.

“This is exactly what we do not need in our politics right now: negative, personal attacks,” Gifford said in the video.

The video cuts together different scenes — such as Gifford saying he might know more people in Los Angeles or Washington, D.C. than he does in Boston — from the 10-part documentary, although it does not indicate who produced it.

Markwith’s tweet describes it as a “troubling video” and tagged the Massachusetts Democratic Party, several media outlets and both Dan Koh and Barbara L’Italien, two of Gifford’s opponents in the primary. His page is set to private, but The Sun acquired a screenshot of the initial tweet.

Markwith could not be reached Monday for comment.

Kerrigan, who dropped out of the race in February, and later endorsed L’Italien, retweeted the video. That tweet is no longer visible, but could be found Monday afternoon on a Google cached version of Kerrigan’s feed.

Markwith and Kerrigan had connected before: when Kerrigan was running for lieutenant governor in 2013 and 2014, Markwith gave him a combined $1,000, according to OCPF records.

Reached by The Sun Monday afternoon, Kerrigan said he had no involvement beyond retweeting the link to the video. He did not know its origins, but said it “definitely” was not originally made by Markwith.

“I know nothing more about it other than that I saw it and retweeted it,” Kerrigan said.

On Monday evening, Kerrigan tweeted that he believes the race should not focus on critical ads.

“This election simply has to be about what’s going on right now in DC & what the future will be for the people of #ma3 & this country,” Kerrigan wrote. “Negative attacks about things in the past shouldn’t distract us. The stakes are too high for that kind of nonsense.”

Follow Chris on Twitter @ChrisLisinski.