The addition of Kamala Harris to the Democratic ticket provided Joe Biden with the biggest surge of onlineenthusiasm he's seen in the entire campaign, according to data from NewsWhip provided exclusively to Axios.

Why it matters: While Biden has been getting much of his momentum from voters who are opposed to President Trump, rather than excited about him, Harris could stir other voters looking for reasons to turn out.

Driving the news: With the addition of Harris to the ticket, Biden's campaign picked up some much-needed voter enthusiasm online.

• Biden stories received 64 million interactions on social media (likes, comments, shares) last week — 35% higher than the next biggest week of his campaign, according to the NewsWhip data.
• The 55 million interactions on stories about Harris were higher than Biden had in any other week.
• Biden's second-most engaged tweet of the campaign was his announcement of Harris last Tuesday (1.02m engagements), according to data from KeyHole. (Number one was "I can't believe I have to say this, but please don't drink bleach," in response to Trump's April suggestion that injecting disinfectant might be a way to fight the coronavirus.)

The big picture: 58% of voters who say they'll vote Biden are doing so out of opposition to Trump rather than in support of the Democratic candidate, according to a recent Wall Street Journal/NBC News poll.

• For the 36% who are "more for Joe Biden" than "against Donald Trump", Kamala Harris on the ticket could make a difference in whether they actually show up to vote.

Harris may help to inspire voters that are interested in policy issues like police reform, social justice and women's rights — issues where her tweets have gotten more online traction than Biden's. Voters interested in these issues are a powerful voice on social media and could help amplify overall the ticket online. 

• In 2016, Black voter turnout dropped to 56% from 62% in 2012.
• The Black Lives Matter protests around the country have inspired millions of Americans to speak up in favor of criminal justice and police reform, issues that Harris has been outspoken about online.

By the numbers: While Trump's online numbers dwarf Biden's, the combination of Biden and Harris closes the gap compared to Trump and Mike Pence.

• Harris has as many Instagram followers as Biden (3.3m) and is much closer to the presidential nominee on Twitter and Facebook than Pence is to Trump.
• She also packs a consistent punch online. In the months leading up to Biden's running mate selection, Harris generated more social media interaction than any of the other top VP contenders.

Harris' online following is loyal and hyperactive online. In 2018, supporters started posting about Harris using the hashtag #KHive. The #KHive fan following has gone viral, and is made up mostly of women of color and their allies supporting Harris' run and her policies.

• Few other politicians have loyal followings online, with the exceptions of Trump's #MAGA followers, Bernie Sanders devotees and the #YangGang.

Harris could also help inspire social change-makers on social media if she builds enthusiasm for the ticket among Black voters.Black social media users tend to be far more civically engaged online than white social media users, according to the Pew Research Center.

• Nearly half (48%) of Black social media users say they have posted a picture on social media to show their support for a cause in the past month, compared with 37% of Hispanic users and 33% of white users.
• Black users are also more than twice as likely as white users to say they have used a hashtag related to a political or social issue on these platforms in the past month.

Yes, but: Biden's attention deficit to Trump may not be such a disadvantage. He's grown his national polling average lead to 8 points, per FiveThirtyEight, while generating 6x less online buzz than Trump over the past few months, according to NewsWhip data.