KHive

Origins.
Sources vary on the coinage of the term. "The Daily Dot" said Joy Reid first used the term in August 2017 in a tweet saying "@DrJasonJohnson @ZerlinaMaxwell and I had a meeting and decided it's called the K-Hive." Reecie Colbert, a prominent member of the movement, told Bakari Sellers she believed Bianca Delarosa coined the term but disputed a claim by Delarosa that she was “the only one who speaks for KHive.” She said the movement had no formal leaders but was "just a bunch of really scrappy accounts on Twitter, on social media." 
Usage of the hashtag increased in August 2018, before Harris had announced her presidential candidacy but after she told MSNBC's Kasie Hunt that she was "not ruling it out." As of July 2019, while Harris was in her presidential campaign, 38,000 Twitter accounts had used the hashtag and according to "Vox" "accrued an estimated 360 million impressions". The hashtag is a reference to #BeyHive, which is a group of Beyoncé fans.
The movement has been cited as an example of social media fandom or stan culture.
Activity.
The community formed prior to and during Harris's 2020 presidential campaign as an effort to defend her from racist and sexist attacks and debunk misinformation. It is not formally affiliated with the campaign.
Organizing platform Mobilize said Harris' digital team "was able to draw her community of online supporters, also known as the KHive, off the internet and into the volunteer ecosystem, where they could advocate on behalf of the campaign, call potential voters, and host events". 
When Harris endorsed Joe Biden in March 2020, the Biden campaign released a video in which Biden asks Harris if the #KHive will support him.
According to "Wired", the organization was expected to be helpful to the 2020 Biden-Harris campaign. According to Newsy, the strength of the relationship between KHive and Harris could be used to force Biden to take Harris' point of view seriously. Kimberly Peeler-Allen of Rutgers' Center for American Women and Politics told Newsy that "the urge to stick with the status quo and the same voices around the table is extremely strong, so it will take the #KHive and coalition work all across the board to make sure that Senator Harris' voice is definitely heard and taken into account."
In September 2020, Alanna Vagianos, writing for "The Huffington Post", observed that "as with most loosely-organized online groups, it does not have a unified set of tactics, and bad actors are hard or impossible to control." According to Vagianos, there have been claims by supporters of Bernie Sanders and Elizabeth Warren that they have been cyber-harassed by individuals alleged to be affiliated with the KHive. In response to the Huffington Post article, Sabrina Singh, the press secretary for Kamala Harris, stated "The campaign does not condone doxxing, derogatory language or harassment of any kind." Some progressives have argued that there is a double standard regarding KHive from the media and some Democrats due to the substantial amount of criticism that supporters of Bernie Sanders labeled as "Bernie Bros" received for allegations of harassment.
Related hashtags.
Harris's supporters also use the hashtag #WeGotHerBack. Followers of her husband on social media call themselves the #DougHive.