Robert F. Kennedy Jr. is expected to announce on Tuesday that Nicole Shanahan, a Silicon Valley lawyer, investor and political neophyte, will be his running mate in his independent presidential bid, according to two people close to the campaign.

The formal announcement, set to take place in Oakland, Calif., ends a wide-ranging and eclectic search for a vice-presidential nominee. Even in the past few weeks, it had evolved as Mr. Kennedy and his advisers spoke with more than half a dozen prospective candidates.

A spokeswoman for Mr. Kennedy’s campaign declined to comment. Mr. Kennedy and Ms. Shanahan did not respond to requests for comment on Monday evening.

Ms. Shanahan, 38, was a late-breaking favorite in Mr. Kennedy’s search, according to the two people close to the campaign, though she has been publicly associated with his candidacy since she helped pay for a Super Bowl ad in support of him.

This month, The New York Times reported that Aaron Rodgers, the N.F.L. quarterback, and Jesse Ventura, the former Minnesota governor and onetime professional wrestler, were at the top of Mr. Kennedy’s list.

Mr. Kennedy confirmed those names in an interview at the time, adding that he had been in discussions with several others, including Scott Brown, the Republican former senator from Massachusetts; Tricia Lindsay, a lawyer who has fought vaccine mandates; and Tulsi Gabbard, the former congresswoman from Hawaii and presidential candidate who left the Democratic Party to become an independent.

Mr. Kennedy and his top advisers also spoke with Mike Rowe, the host of the reality television show “Dirty Jobs,” according to one of the people familiar with the campaign. Mr. Rowe has since addressed those discussions in interviews.

Mr. Rowe was among the people mentioned by Amaryllis Fox Kennedy, Mr. Kennedy’s daughter-in-law and campaign manager, in a social media post on March 16 addressing the reports of possible running mates. She also mentioned Mr. Rodgers and Ms. Shanahan. Mediaite first reported the same day that Ms. Shanahan was the expected choice.

Mr. Kennedy had been on the clock to name a vice-presidential pick because some states require a full ticket to be on the petition for independent candidates to be placed on the ballot.

Ms. Shanahan, who was once married to the Google co-founder Sergey Brin, has a history of making donations to Democratic campaigns, including to President Biden’s 2020 run. But she gave to Mr. Kennedy’s presidential campaign in May 2023, when he was running as a Democrat.

Mr. Kennedy announced in October that he would instead run as an independent, saying that the Democratic Party had corruptly blocked his efforts to challenge Mr. Biden in the primaries. Ms. Shanahan said in an interview with The Times last month, after she disclosed her role in the Super Bowl ad, that his decision to leave the party had initially disappointed her, and that she had stepped back from supporting him.

But she came around again at the beginning of the year, she said, after finding “pockets of silent support all over the place.”

She added, “It was very, very interesting to me to hear how people have been kind of stirred by his message and his willingness to be out there.”

Mr. Kennedy, 70, an environmental lawyer and member of a storied Democratic political family, has in recent years been a prominent broadcaster of vaccine skepticism and conspiracy theories as part of a broad anti-establishment message.

The Democratic Party has increasingly focused legal and organizational resources on combating Mr. Kennedy — in particular, his efforts to get on state ballots — seeing his candidacy as one of the greatest threats to Mr. Biden’s re-election.

A recent Fox News national poll put Mr. Kennedy’s support at around 13 percent, drawing a roughly equal share of voters away from both Mr. Biden and former President Donald J. Trump. But Democrats are worried that more choices hurt Mr. Biden, and are less likely to erode Mr. Trump’s loyal base of support.

In her interview with The Times, Ms. Shanahan said that she was “not an anti-vaxxer,” adding that vaccines had historically been a “very helpful” part of public health measures. But she suggested some alignment with theories falsely linking certain childhood vaccinations with autism and other ailments, saying: “I do think that the increase of vaccine-related injuries is very alarming, and I do think we need to understand the screening mechanisms.”