Independent presidential candidate Robert F. Kennedy Jr. is officially a bigger threat to President Biden than President Trump.

That was the message Tuesday in Oakland, California, where Mr. Kennedy announced that his vice-presidential running mate will be Silicon Valley attorney and tech entrepreneur Nicole Shanahan. Democrats are worried.

Ms. Shanahan is a 38-year-old frequent donor to Democrats like Mayor Pete Buttigieg. She’s a former wife to Google co-founder Sergey Brin. Ms. Shanahan has deep pockets and appeals to younger, tech-savvy voters, those worried about, say, environmental and food contaminants and Democrats disillusioned with the party.

Mr. Kennedy’s speech and the campaign video shown prior to Ms. Shanahan taking the stage highlighted her youth, her physical fitness, her love of surfing and the environment, and her pro-choice views.

“I am leaving the Democratic Party,” Ms. Shanahan told the crowd. “Even though I’m leaving the party, I believe I’m taking the best ideals and impulses with me.”   

Ms. Shanahan spoke about her poor upbringing as the daughter of immigrants, her work for criminal justice reform, and her time in tech. She also spoke about her young daughter with autism and dipped her toes into the vaccine debate by mentioning “medicines” as one of the causes of the disorder.

“She understands that the health of every American is a national security issue,” Mr. Kennedy said. “I wanted an advocate who has seen corruption of our regulatory authorities firsthand and shares my indignation about the way it allows regulated industries to commoditize our landscapes, our food, our wildlife, and our children.”

Were there any doubt before this announcement about from which party a Kennedy-Shanahan ticket would draw more votes, the land acknowledgment by members of the Muwekma Ohione tribe at the beginning of the event settled the matter.

The two-and-a-half-hour campaign event also featured a video appealing to African American voters and a tribal faith leader chanting. The event’s livestream chat box was filled with a mix of comments from “this is incredibly beautiful” to “cringe lol” and a coarse reference to being “woke.”

The range of reactions speaks to Mr. Kennedy’s appeal across party and ideological lines. His support for strong border security and his staunch advocacy for free speech and against lockdowns have earned him support among center right voters and libertarians.

A Stanford medical professor, Dr. Jay Bhattacharya, co-author of the Great Barrington Declaration, spoke at the event about free speech and the harms caused by Covid lockdowns. A former chief for the United States Border Patrol also spoke.

Mr. Kennedy has actively courted libertarians, and his campaign has not ruled out seeking the Libertarian nomination at the party’s convention in May. Ballot access is one of the Kennedy campaign’s biggest challenges, and the Libertarian Party expects to have ballot access in “worst case scenario would be 48 states,” the party’s chairwoman, Angela McArdle, tells the Sun.

By picking Ms. Shanahan, though, Mr. Kennedy is sticking to his Democratic Party roots. “It means he’s decided to target Biden, because there’s not going to be anybody on the center right to say MAGA people who are even going to be slightly tempted by Shanahan at all,” a libertarian economist and author, Jeffrey Tucker, tells the Sun.

“But that’s not a crazy decision because if you look at RFK, his writings, he’s very interested in rescuing what he calls liberalism from corporatism,” Mr. Tucker says. “His main objective is not so much to appeal to Republicans. His passion is to save what he considers to be American liberalism of his father and his uncle.”

Some large Republican accounts online celebrated Mr. Kennedy’s vice-presidential pick because he’s now less of a threat to Mr. Trump. Several large libertarian accounts lamented Mr. Kennedy’s choice. 

“Pretty neat how RFK Jr came out the gate spitting hard truths and looked like he could be a legit contender,” a libertarian podcaster, Clint Russell, posted to X. “Either he was threatened or he is the most tone deaf politician in my lifetime.”

Since leaving the Democratic Party in October, Mr. Kennedy has run the most successful independent presidential campaign since Ross Perot in 1992. In that election, Perot earned 18 percent of the vote and helped propel Bill Clinton to the White House. Mr. Kennedy is polling on average at 12 percent.

With younger Americans, Mr. Kennedy polls even higher. In key swing states, where the 2024 election will likely be decided, Mr. Kennedy beats both Messrs. Trump and Biden among Americans ages 18 to 44, according to a New York Times/Sienna poll.

Mr. Kennedy often cites this poll and his support among Millennials and Generation Z when he’s campaigning. Choosing Ms. Shanahan, a Millennial in the tech world, as his running mate is a clear play to try to excite these voters — an important demographic for Democrats as well.

After the Kennedy campaign event wrapped up, the Democratic National Committee held a Zoom response with reporters that featured three young Democratic politicians who represent the key demographic groups of the party: an African American, a Latino, and a white woman.

After failing to take third-party challengers seriously in 2016 — arguably costing Hillary Clinton the election — the Democratic National Committee has reportedly created a whole unit to deal with third-party challengers this cycle.

“This is a person that is a tinfoil hat conspiracy theorist,” a Democratic congressman, Robert Garcia, said on the Zoom call. “And his vice-presidential pick essentially just doubles down on these anti-vaccine conspiracies, anti-health agenda that is quite frankly dangerous.”

“He picked a VP who can fund, who can buy his way onto the ballot in a number of states,” a Democratic state senator from Michigan, Mallory McMorrow, said. “We cannot afford Donald Trump to be back in the White House, which is what is going to happen if people don’t see RFK for what he actually is, which is Donald Trump with a Kennedy name slapped on him.”